BUG:343837 Don't assert when checking the texture option

The assert is meant to warn us that some option is emitting changes
to the settings while writing the settings. The texture option does
exactly that because if you check for the currently set pattern, and
no pattern is set (which can happen because of the background loading of
patterns), it will set a pattern. Which will cause the settings to
change as they are being written.

So block all pattern resource chooser signals while writing out the
option -- the written option will be correct anyway.