Clearing array with setting length to 0 replaced with [] for being short
and marginally efficient. For reference: [] is turned into a sequence of
around 15 machine instructions on x64 (if bump pointer allocation succeeds),
whereas a.length=0 is a C++ runtime function call, which requires 10-100x as
many instructions.
Benedikt Meurer
PR Close#20395
Update to in-memory-web-api should handle id=0.
Make sure this works by having a hero with id=0 in ToH.
Coincidentally delete lingering dead app/ folders
Todo: fix ToH images (which have to do anyway)
