Catch if the set default colormap hasn't been loaded

Author: rosswhitfield

qt/python/mantidqt/mantidqt/widgets/colorbar/colorbar.py

@@ -182,7 +182,11 @@ def set_mappable(self, mappable):
         self.colorbar = Colorbar(ax=self.ax, mappable=mappable)
         self.cmin_value, self.cmax_value = mappable.get_clim()
         self.update_clim_text()
-        self.cmap_changed(cmap, False)
+        try:
+            self.cmap_changed(cmap, False)
+        except ValueError:
+            # the default mantid colormap is not available, just use matplotlib default
+            pass
 
         mappable_cmap = get_current_cmap(mappable)