Fix the problem where trying to digitise on an empty map never gave

visible features. ZoomFullExtent now only does that if the 'full
extent' is not an empty extent (zero width/height). This was possibly
part of the problem in ticket #219


git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@5671 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: g_j_m

src/gui/qgsmapcanvas.cpp

@@ -414,7 +414,10 @@ void QgsMapCanvas::clear()
 
 void QgsMapCanvas::zoomFullExtent()
 {
-  setExtent(fullExtent());
+  QgsRect extent = fullExtent();
+  // If the full extent is an empty set, don't do the zoom
+  if (!extent.isEmpty())
+    setExtent(extent);
   refresh();
 
 } // zoomFullExtent