#568 GMap - maptype duplicates

[conw]

After editing a new maptype and clicking the save button, the "loading window" appears, seemingly eternally. Sometimes, this also happens when adding markers. Clicking a second time finally adds the marker and kills the "loading window". But doing so when saving a new maptype saves a duplicate for every extra click. At least maptype names should be unique because they appear in comboboxes for public.