[MC-109593] Debug world spamming "Tried to assign a mutable BlockPos to a block entity" warnings

Affects any version 1.10.2 and forward, in a Debug world. Not sure about 1.10.1, since that was the crashing one.

Doesn't matter in what version the world was created. Happens in any gamemode, Spectator included.

Just open the world, and the following is spammed in the Game Output:

[17:00:46] [Chunk Batcher 4/WARN]: Tried to assign a mutable BlockPos to a block entity...
java.lang.Error: class co$a
	at arz.a(SourceFile:259) [16w44a.jar:?]
	at aul.a(SourceFile:657) [16w44a.jar:?]
	at ajp.a(SourceFile:1941) [16w44a.jar:?]
	at aul.a(SourceFile:636) [16w44a.jar:?]
	at ajy.a(SourceFile:68) [16w44a.jar:?]
	at ajy.r(SourceFile:60) [16w44a.jar:?]
	at bey$5.a(SourceFile:51) [16w44a.jar:?]
	at bey.a(SourceFile:189) [16w44a.jar:?]
	at bqz.a(SourceFile:238) [16w44a.jar:?]
	at bqz.c(SourceFile:113) [16w44a.jar:?]
	at bqz.a(SourceFile:51) [16w44a.jar:?]
	at bqz.a(SourceFile:42) [16w44a.jar:?]
	at bqx.a(SourceFile:65) [16w44a.jar:?]
	at btb.b(SourceFile:178) [16w44a.jar:?]
	at bsx.a(SourceFile:100) [16w44a.jar:?]
	at bsx.run(SourceFile:43) [16w44a.jar:?]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_25]

Submitted in case this indicates a wider issue than just a debug-world thing.