Bug 1879441: Added null check for selections in nsINode::IsSelected()…

…. a=diannaS

Selections are stored here as WeakPtr to save refcount overhead, which means that a selection can be null.

Original Revision: https://phabricator.services.mozilla.com/D202143

Differential Revision: https://phabricator.services.mozilla.com/D202146

dom/base/nsINode.cpp

@@ -359,7 +359,9 @@ bool nsINode::IsSelected(const uint32_t aStartOffset,
       // Looks like that IsInSelection() assert fails sometimes...
       if (range->IsInAnySelection()) {
         for (const WeakPtr<Selection>& selection : range->GetSelections()) {
-          ancestorSelections.Insert(selection);
+          if (selection) {
+            ancestorSelections.Insert(selection);
+          }
         }
       }
     }