Shift + F3 Crash

In a superflat world, I went to hold down shift + F3 so the bottom-right profiler pie graph would come up. But instead, Minecraft crashed. I quickly skimmed through the report, and it thinks the game is most likely modded,even though this is a clean 1.4.3 jar. Pressing only F3 doesn't seem to crash the game though.

---- Minecraft Crash Report ----
// I feel sad now :(

Time: 2/11/12 6:14 PM
Description: Ticking entity

java.lang.NullPointerException
	at bed.b(SourceFile:188)
	at beb.a(SourceFile:62)
	at py.j_(SourceFile:274)
	at xv.a(SourceFile:1315)
	at xv.g(SourceFile:1294)
	at xv.h(SourceFile:1194)
	at net.minecraft.client.Minecraft.l(SourceFile:1283)
	at net.minecraft.client.Minecraft.J(SourceFile:582)
	at net.minecraft.client.Minecraft.run(SourceFile:534)
	at java.lang.Thread.run(Unknown Source)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at bed.b(SourceFile:188)
	at beb.a(SourceFile:62)
	at py.j_(SourceFile:274)
	at xv.a(SourceFile:1315)
	at xv.g(SourceFile:1294)

-- Entity being ticked --
Details:
	Entity Type: Minecart (py)
	Entity ID: 83668
	Name: Minecart
	Exact location: -1046.50, 5.19, -419.38
	Block location: World: (-1047,5,-420), Chunk: (at 9,0,12 in -66,-27; contains blocks -1056,0,-432 to -1041,255,-417), Region: (-3,-1; contains chunks -96,-32 to -65,-1, blocks -1536,0,-512 to -1025,255,-1)
	Momentum: 0.00, 0.00, 0.00
Stacktrace:
	at xv.h(SourceFile:1194)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [ayh['Apocalypsing'/83714, l='MpServer', x=-1122.60, y=7.03, z=-407.21]]
	Chunk stats: MultiplayerChunkCache: 441
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-989,4,-304), Chunk: (at 3,0,0 in -62,-19; contains blocks -992,0,-304 to -977,255,-289), Region: (-2,-1; contains chunks -64,-32 to -33,-1, blocks -1024,0,-512 to -513,255,-1)
	Level time: 2180249 game time, 98145 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
	Forced entities: 51 total; [qo['Slime'/83403, l='MpServer', x=-1187.69, y=1.00, z=-423.41], ox['Bat'/83404, l='MpServer', x=-1122.73, y=8.26, z=-353.82], qo['Slime'/106576, l='MpServer', x=-1182.22, y=5.00, z=-328.11], qo['Slime'/83409, l='MpServer', x=-1113.33, y=4.50, z=-372.19], qo['Slime'/176342, l='MpServer', x=-1121.10, y=4.85, z=-426.03], qo['Slime'/149946, l='MpServer', x=-1068.22, y=2.00, z=-396.78], qo['Slime'/83415, l='MpServer', x=-1087.58, y=6.04, z=-372.25], ayh['Apocalypsing'/83714, l='MpServer', x=-1122.60, y=7.03, z=-407.21], ox['Bat'/83414, l='MpServer', x=-1126.66, y=10.08, z=-387.65], qo['Slime'/83416, l='MpServer', x=-1069.59, y=4.00, z=-405.25], qo['Slime'/471718, l='MpServer', x=-1066.62, y=4.69, z=-330.78], px['item.item.slimeball'/83424, l='MpServer', x=-1151.63, y=4.13, z=-435.78], py['Minecart'/83668, l='MpServer', x=-1046.50, y=5.19, z=-419.38], qo['Slime'/83425, l='MpServer', x=-1118.49, y=4.00, z=-335.11], qo['Slime'/83426, l='MpServer', x=-1171.69, y=1.00, z=-398.72], qo['Slime'/562793, l='MpServer', x=-1100.42, y=4.47, z=-383.45], qo['Slime'/242736, l='MpServer', x=-1101.48, y=4.00, z=-455.16], qo['Slime'/83435, l='MpServer', x=-1113.22, y=4.50, z=-368.22], qo['Slime'/83436, l='MpServer', x=-1106.63, y=3.80, z=-373.63], qo['Slime'/83438, l='MpServer', x=-1059.13, y=5.03, z=-416.25], qo['Slime'/83439, l='MpServer', x=-1192.38, y=4.00, z=-364.16], qo['Slime'/182284, l='MpServer', x=-1186.38, y=1.00, z=-422.63], px['item.item.slimeball'/83424, l='MpServer', x=-1151.63, y=4.13, z=-435.78], qo['Slime'/482118, l='MpServer', x=-1083.96, y=5.00, z=-382.93], qo['Slime'/484817, l='MpServer', x=-1111.36, y=4.50, z=-404.60], qo['Slime'/211056, l='MpServer', x=-1100.47, y=4.95, z=-387.55], qo['Slime'/516370, l='MpServer', x=-1146.86, y=5.00, z=-353.31], qo['Slime'/563601, l='MpServer', x=-1089.50, y=4.00, z=-377.50], qo['Slime'/223565, l='MpServer', x=-1069.63, y=4.47, z=-343.70], pe['Pig'/83635, l='MpServer', x=-1070.75, y=2.00, z=-396.50], pe['Pig'/83634, l='MpServer', x=-1072.94, y=4.00, z=-462.94], qo['Slime'/561868, l='MpServer', x=-1113.74, y=4.96, z=-385.84], qo['Slime'/202657, l='MpServer', x=-1064.72, y=4.00, z=-338.50], qo['Slime'/301010, l='MpServer', x=-1087.26, y=4.00, z=-431.18], qo['Slime'/83751, l='MpServer', x=-1169.86, y=4.47, z=-407.99], qo['Slime'/83750, l='MpServer', x=-1172.94, y=1.00, z=-393.63], qo['Slime'/181676, l='MpServer', x=-1118.69, y=4.00, z=-471.87], qo['Slime'/442165, l='MpServer', x=-1153.09, y=4.00, z=-375.34], qo['Slime'/471233, l='MpServer', x=-1119.24, y=4.00, z=-407.86], oz['Chicken'/83761, l='MpServer', x=-1178.06, y=4.00, z=-396.31], qo['Slime'/85389, l='MpServer', x=-1127.52, y=4.33, z=-407.04], qo['Slime'/98113, l='MpServer', x=-1187.63, y=4.00, z=-358.91], qo['Slime'/403958, l='MpServer', x=-1137.10, y=4.59, z=-473.89], qo['Slime'/98670, l='MpServer', x=-1100.95, y=4.93, z=-369.78], qo['Slime'/561218, l='MpServer', x=-1107.60, y=4.47, z=-385.51], qo['Slime'/347026, l='MpServer', x=-1115.00, y=4.00, z=-334.35], qo['Slime'/279197, l='MpServer', x=-1197.48, y=4.95, z=-468.24], qo['Slime'/283326, l='MpServer', x=-1151.30, y=4.00, z=-342.14], qo['Slime'/355624, l='MpServer', x=-1085.22, y=4.00, z=-436.63], qo['Slime'/283323, l='MpServer', x=-1175.35, y=3.00, z=-356.92], qo['Slime'/191146, l='MpServer', x=-1187.24, y=1.90, z=-424.96]]
	Retry entities: 0 total; []
Stacktrace:
	at aye.a(SourceFile:290)
	at net.minecraft.client.Minecraft.b(SourceFile:1828)
	at net.minecraft.client.Minecraft.run(SourceFile:543)
	at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
	Minecraft Version: 1.4.3
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.6.0_37, Sun Microsystems Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Sun Microsystems Inc.
	Memory: 97199440 bytes (92 MB) / 205389824 bytes (195 MB) up to 1908932608 bytes (1820 MB)
	JVM Flags: 2 total; -Xms128M -Xmx2048M
	AABB Pool Size: 1391 (77896 bytes; 0 MB) allocated, 776 (43456 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	LWJGL: 2.8.4
	OpenGL: ATI Mobility Radeon HD 3650 GL version 3.3.11653 Compatibility Profile Context, ATI Technologies Inc.
	Is Modded: Very likely; Jar signature invalidated
	Type: Client (map_client.txt)
	Texture Pack: Default
	Profiler Position: root.tick.level.entities.regular.tick
	Vec3 Pool Size: 336 (18816 bytes; 0 MB) allocated, 111 (6216 bytes; 0 MB) used