tl;dr: I fucking suck at coding (fix double free)

MRI: Filesystem: A garbage collected SDL_RWops file handle
will call close on itself even if 'close' was explicitly
called on it on the script side before.

src/filesystem.cpp

@@ -117,6 +117,7 @@ static int SDL_RWopsClose(SDL_RWops *ops)
 		return -1;
 
 	int result = PHYSFS_close(f);
+	ops->hidden.unknown.data1 = 0;
 
 	return (result != 0) ? 0 : -1;
 }