Hey there! Looks like this was an oversight on my end, with a fix intended to fix something Ren'Py bungled in v8.4. You can make the following change in the common file, to new_renpy_loadable:
if renpy.version_tuple >= (8, 4, 0) and renpy.version_tuple < (8, 4, 2):
## There's a problem with how renpy.loadable works with empty strings
old_renpy_loadable = renpy.loadable
def new_renpy_loadable(s, **kwargs):
if s == "":
return False
return old_renpy_loadable(s, **kwargs)
renpy.loadable = new_renpy_loadable
Hope that helps!