Firework Rockets do not spawn (with both command blocks and the item).
[20:42:33] [Client thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_25]
at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_25]
at h.a(SourceFile:46) [16w32b.jar:?]
at bdo.av(SourceFile:959) [16w32b.jar:?]
at bdo.a(SourceFile:395) [16w32b.jar:?]
at net.minecraft.client.main.Main.main(SourceFile:124) [16w32b.jar:?]
Caused by: java.lang.NullPointerException
at aar.<init>(SourceFile:52) ~[16w32b.jar:?]
at bmc.a(SourceFile:318) ~[16w32b.jar:?]
at fp.a(SourceFile:122) ~[16w32b.jar:?]
at fp.a(SourceFile:13) ~[16w32b.jar:?]
at fn$1.run(SourceFile:13) ~[16w32b.jar:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_25]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_25]
at h.a(SourceFile:45) ~[16w32b.jar:?]
... 3 more
I can confirm this happens for me in 16w32a and 16w32b. There's no firework rocket entity shown, but the launch sound is heard. There's also no explosion (sound or particles) for those that should have one (my particles are set to 'All').