If you enter a command in the command block:
/setblock ~ ~1 ~ minecraft:hopper 6/setblock ~ ~1 ~ minecraft:hopper 6Game crashed. And world becomes unavailable.
When approaching game Crashed.File crash-report Attachment.
Description: Ticking block entity
java.lang.ArrayIndexOutOfBoundsException: 6
at ann.l(SourceFile:325)
at ann.k(SourceFile:174)
at ann.i(SourceFile:160)
at ann.h(SourceFile:152)
at afk.h(SourceFile:1286)
at mi.h(SourceFile:364)Description: Ticking block entity
java.lang.ArrayIndexOutOfBoundsException: 6
at ann.l(SourceFile:325)
at ann.k(SourceFile:174)
at ann.i(SourceFile:160)
at ann.h(SourceFile:152)
at afk.h(SourceFile:1286)
at mi.h(SourceFile:364)
Don't do that.