When summoniing a cartographer with this command:
/summon villager ~ ~ ~ {Profession:1,Career:2,CareerLevel:3}
It will crash you when you try to open the villager, as well as some cartographers found naturally won't upgrade to a woodland mansion or sea temple map at all.
[08:38:36] [Server thread/WARN]: Exception loading entity:
h: Loading entity NBT
at aie.f(SourceFile:1593) ~[1.13-pre1.jar:?]
at aii.a(SourceFile:367) ~[1.13-pre1.jar:?]
at bqx.a(SourceFile:775) [1.13-pre1.jar:?]
at bqx.a(SourceFile:723) [1.13-pre1.jar:?]
at bqx.a(SourceFile:753) [1.13-pre1.jar:?]
at rf.a(SourceFile:64) [1.13-pre1.jar:?]
at rf.a(SourceFile:45) [1.13-pre1.jar:?]
at rf$$Lambda$1365/1200592701.run(Unknown Source) [1.13-pre1.jar:?]
at com.mojang.brigadier.CommandDispatcher.execute(CommandDispatcher.java:128) [brigadier-0.1.27.jar:?]
at com.mojang.brigadier.CommandDispatcher.execute(CommandDispatcher.java:68) [brigadier-0.1.27.jar:?]
at bu.a(SourceFile:202) [1.13-pre1.jar:?]
at tl.c(SourceFile:830) [1.13-pre1.jar:?]
at tl.a(SourceFile:817) [1.13-pre1.jar:?]
at mc.a(SourceFile:37) [1.13-pre1.jar:?]
at mc.a(SourceFile:9) [1.13-pre1.jar:?]
at iu$1.run(SourceFile:13) [1.13-pre1.jar:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_25]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_25]
at k.a(SourceFile:148) [1.13-pre1.jar:?]
at net.minecraft.server.MinecraftServer.w(SourceFile:670) [1.13-pre1.jar:?]
at net.minecraft.server.MinecraftServer.v(SourceFile:626) [1.13-pre1.jar:?]
at dio.v(SourceFile:156) [1.13-pre1.jar:?]
at net.minecraft.server.MinecraftServer.run(SourceFile:531) [1.13-pre1.jar:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_25]
Caused by: com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1 path $
at com.google.gson.internal.Streams.parse(Streams.java:60) ~[gson-2.8.0.jar:?]
at com.google.gson.internal.bind.TreeTypeAdapter.read(TreeTypeAdapter.java:65) ~[gson-2.8.0.jar:?]
at wt.a(SourceFile:493) ~[1.13-pre1.jar:?]
at wt.a(SourceFile:518) ~[1.13-pre1.jar:?]
at ig$a.a(SourceFile:243) ~[1.13-pre1.jar:?]
at aie.f(SourceFile:1568) ~[1.13-pre1.jar:?]
... 23 more
Caused by: com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1 path $
at com.google.gson.stream.JsonReader.syntaxError(JsonReader.java:1559) ~[gson-2.8.0.jar:?]
at com.google.gson.stream.JsonReader.checkLenient(JsonReader.java:1401) ~[gson-2.8.0.jar:?]
at com.google.gson.stream.JsonReader.doPeek(JsonReader.java:593) ~[gson-2.8.0.jar:?]
at com.google.gson.stream.JsonReader.peek(JsonReader.java:425) ~[gson-2.8.0.jar:?]
at com.google.gson.internal.Streams.parse(Streams.java:46) ~[gson-2.8.0.jar:?]
at com.google.gson.internal.bind.TreeTypeAdapter.read(TreeTypeAdapter.java:65) ~[gson-2.8.0.jar:?]
at wt.a(SourceFile:493) ~[1.13-pre1.jar:?]
at wt.a(SourceFile:518) ~[1.13-pre1.jar:?]
at ig$a.a(SourceFile:243) ~[1.13-pre1.jar:?]
at aie.f(SourceFile:1568) ~[1.13-pre1.jar:?]
... 23 more
[08:38:36] [Client thread/INFO]: [CHAT] Unable to summon entity
Linked issues
relates to 1
Attachments
Comments

Added
For me, this happened when I gave myself an armor stand with NBT (Marker:1b, Custom Name, CustomNameVisible) with a wrong (outdated) command (without all that escaping and quotation marks we now need) and tried to place it.
It did not crash me, it just gave me "Fatal" errors in the log, saying "Error executing task" > "Loading entity NBT". Does this belong into this bugpost here as well? I didn't find anything when I was searching (but as everyone knows, I suck at finding them).
[media]

Doesn't crash in 1.13-pre5. You cannot open the villagers gui though

Can confirm the fix.
Unsure if the not opening gui is a new issue.
Incomplete without a crash report from (minecraft/crash-reports/crash-<DATE>-client.txt). Please attach it to this ticket so that we can diagnose your issue.