Fixed histogram display range reset on 3D histogram overlay

enabling. Was caused by bug in the props bindable module.

fsl/fslview/displaycontext/displaycontext.py

@@ -119,6 +119,8 @@ class DisplayContext(props.SyncableHasProperties):
                 dParent = None
             else:
                 dParent = self.getParent().getDisplay(overlay, overlayType)
+                if overlayType is None:
+                    overlayType = dParent.overlayType
                 
             display = fsldisplay.Display(overlay,
                                          self.__overlayList,

fsl/fslview/views/histogrampanel.py

@@ -162,11 +162,8 @@ class HistogramSeries(plotpanel.DataSeries):
 
             self.overlayList.append(self.overlay3D)
 
-            print 'Appended new mask overlay'
             opts = self.displayCtx.getOpts(self.overlay3D, overlayType='mask')
 
-            print 'Got overlay options'
-
             opts.bindProps('volume',    self)
             opts.bindProps('colour',    self)
             opts.bindProps('threshold', self, 'dataRange')
@@ -250,6 +247,7 @@ class HistogramPanel(plotpanel.PlotPanel):
         """De-registers property listeners. """
         plotpanel.PlotPanel.destroy(self)
 
+        self.removeGlobalListener(self._name)
         self._overlayList.removeListener('overlays',        self._name)
         self._displayCtx .removeListener('selectedOverlay', self._name)