Sometimes profile.mouseUp handlers will be called without a prior call

to profile.mouseDown/Drag

fsl/fslview/gl/globject.py

@@ -61,12 +61,12 @@ class GLObject(object):
         this instance, ``name``, which is simply a unique name for this
         instance.
 
-        Subclass implementations should call this method, and should perform
-        any necessary OpenGL initialisation, such as creating textures.
+        Subclass implementations must call this method, and should also
+        perform any necessary OpenGL initialisation, such as creating
+        textures.
         """
 
         self.name = '{}_{}'.format(type(self).__name__, id(self))
-
         self.__updateListeners = {}
 
         

fsl/fslview/profiles/orthoviewprofile.py

@@ -70,6 +70,11 @@ class OrthoViewProfile(profiles.Profile):
         self._ycanvas = canvasPanel.getYCanvas()
         self._zcanvas = canvasPanel.getZCanvas()
 
+        # This attribute will occasionally store a
+        # reference to a gl.annotations.Rectangle -
+        # see the _zoomModeLeftMouse* handlers
+        self._lastRect = None
+
 
     def getEventTargets(self):
         """
@@ -229,7 +234,9 @@ class OrthoViewProfile(profiles.Profile):
 
         mouseDownPos, canvasDownPos = self.getMouseDownLocation()
 
-        canvas.getAnnotations().dequeue(self._lastRect)
+        if self._lastRect is not None:
+            canvas.getAnnotations().dequeue(self._lastRect)
+            self._lastRect = None
 
         rectXlen = abs(canvasPos[canvas.xax] - canvasDownPos[canvas.xax])
         rectYlen = abs(canvasPos[canvas.yax] - canvasDownPos[canvas.yax])