Non-standard floating garbage somehow loads in puzzles

[Endaris]

orangetriangle showed an example where things behave (expectedly) weird.
Sample puzzle code:
:pg:
:xx::xx::xx::gtl::gts::gtr:
:xx::xx::xx::gls::ge::grs:
:xx::xx::xx::gbl::gbs::gbr:
:gtl::gts::gtr:
:gls::ge::grs:
:gbl::gbs::gbr:
:xx::pc::xx::pc:
:xx::pc::pr::pr:
:pc::pr::pc::pc:

Non-standard garbage is currently unsupported in puzzles as the syntax requires multi-row garbage to not skip columns.
The validator should catch that and simply refuse to load the puzzle.