Fix for non-gui thread executing GUI code in Mosaic
Fix for non-gui thread executing GUI code in Mosaic

- Fix for Mosaic code having a non-gui thread executing a GUI callback.
  This resulted in QTimer errors.

ejeschke/ginga,pllim/ginga,naojsoft/ginga,naojsoft/ginga,naojsoft/ginga,pllim/ginga,pllim/ginga,ejeschke/ginga,ejeschke/ginga