BUG: Prevent crash in pqDistanceWidget

Added a NULL check for the point properties and the point property
elements to prevent a crash.

Change-Id: I850b7eb3e0d2297959b6fa9e12c2594d849749c4
Merge topic '14620_FixRulerCrash' into next

9c86b790 BUG: Prevent crash in pqDistanceWidget
Improve Visualizer behavior

This change include:
- Hide parent proxy when creating a new filter
- Automatically activate the newly created filter
- Add Opacity control to any filter
- Properly handle domain default properties

Change-Id: I88184734e4e337817743a9a4f9da8b5fbf3e2ee2
Merge topic 'pvweb-visualizer' into next

bfb0af7c Improve Visualizer behavior