Fix invalid iterator deference error
Fix invalid iterator deference error

Error: attempt to dereference a singular iterator.

Objects involved in the operation:
    iterator "this" @ 0x0x7ffbffffa4e0 {
      type = std::__detail::_Node_iterator<std::pair<UnTech::Snes::Tile<16ul> const, UnTech::MetaSprite::Compiler::RomTileData::Accessor const>, false, true> (mutable iterator);
      state = singular;
      references sequence with type 'std::__debug::unordered_map<UnTech::Snes::Tile<16ul>, UnTech::MetaSprite::Compiler::RomTileData::Accessor const, std::hash<UnTech::Snes::Tile<16ul> >, std::equal_to<UnTech::Snes::Tile<16ul> >, std::allocator<std::pair<UnTech::Snes::Tile<16ul> const, UnTech::MetaSprite::Compiler::RomTileData::Accessor const> > >' @ 0x0x5655579937c8
    }

undisbeliever/untech-editor,undisbeliever/untech-editor