The bug
In 1.12.2 /summon used to fail for falling_block if the specified block was not valid:
1.12.2
/summon falling_block ~ ~ ~ {Block:"invalid",Time:-2000}In current versions this is not the case and there is not even an error message in the log.
For endermen the command did not fail unless you provided an invalid short (for example 32768s) but it used the outdated integer id system anyways.
How to reproduce
enderman
Try summoning an
endermanholding an invalid block/summon minecraft:enderman ~ ~ ~ {carriedBlockState:{Name:"minecraft:invalid"}}Try inspecting its
carriedBlockStatetag/data get entity @e[type=enderman,limit=1] carriedBlockState→ ❌ It does not exist
falling_block
Try summoning a
falling_blockentity for an invalid block/summon minecraft:falling_block ~ ~ ~ {BlockState:{Name:"invalid"},Time:-2000}Inspect its
BlockStatetag/data get entity @e[type=falling_block,limit=1] BlockState→ ❌ It defaulted to
sand
Can confirm in 20w51a.