BUG: Consistently handle First/Back/Next/Last keyframe in Endoscopy

This commit ensures that clicking on the Back and Next buttons does not
progress beyond the behavior triggered by clicking on the First and Last
buttons.

Modules/Scripted/Endoscopy/Endoscopy.py

@@ -412,24 +412,32 @@ def onDeleteOrientationButtonClicked(self):
 
     def onFirstOrientationButtonClicked(self):
         allIndices = self.logic.cameraOrientationResampledCurveIndices
+        if not allIndices:
+            return
         whereTo = min(allIndices, default=self.frameSlider.minimum)
         self.frameSlider.value = whereTo
 
     def onBackOrientationButtonClicked(self):
         allIndices = self.logic.cameraOrientationResampledCurveIndices
         allIndices = [x for x in allIndices if x < self.frameSlider.value]
-        whereTo = max(allIndices, default=self.frameSlider.minimum)
+        if not allIndices:
+            return
+        whereTo = max(allIndices)
         self.frameSlider.value = whereTo
 
     def onNextOrientationButtonClicked(self):
         allIndices = self.logic.cameraOrientationResampledCurveIndices
         allIndices = [x for x in allIndices if x > self.frameSlider.value]
-        whereTo = min(allIndices, default=self.frameSlider.maximum)
+        if not allIndices:
+            return
+        whereTo = min(allIndices)
         self.frameSlider.value = whereTo
 
     def onLastOrientationButtonClicked(self):
         allIndices = self.logic.cameraOrientationResampledCurveIndices
-        whereTo = max(allIndices, default=self.frameSlider.maximum)
+        if not allIndices:
+            return
+        whereTo = max(allIndices)
         self.frameSlider.value = whereTo
 
     def onSaveExportModelButtonClicked(self):