Fixed skewed thumbs problem

see issue 701

rtgui/thumbbrowserbase.cc

@@ -539,11 +539,9 @@ void ThumbBrowserBase::refreshThumbImages () {
 		Glib::Mutex::Lock lock(entryMutex);
 		#endif
 
+        int previewHeight = getCurrentThumbSize();
     for (int i=0; i<fd.size(); i++){
-    	previewHeight = getCurrentThumbSize();
     	fd[i]->resize (previewHeight);// TODO!!! Might be performance bottleneck
-		/* called if necessary by resize()
-        fd[i]->refreshThumbnailImage ();  TODO: This might cause crashes on some installations */
     }
 	}
 

rtgui/thumbbrowserentrybase.cc

@@ -254,6 +254,7 @@ void ThumbBrowserEntryBase::getTextSizes (int& infow, int& infoh) {
 }
 
 void ThumbBrowserEntryBase::resize (int h) {
+    if (h==height && drawable) return;  // Short cut if nothing to do
     
     height = h;
     int old_preh = preh;