Sanity check for the "onload" parameter
Sanity check for the "onload" parameter

No idea what "onload" is or why sometimes is a boolean value, but this fixes it.
If this is the correct way, we could replicate this change to lime's AssetsMacro
openfl/openfl,Gama11/openfl,Gama11/openfl,openfl/openfl,Gama11/openfl,openfl/openfl,Gama11/openfl