Bug 1628715 - Part 8: Add MOZ_NONNULL_RETURN to ReconstructElementAt. r=xpcom-reviewers,nika

Differential Revision: https://phabricator.services.mozilla.com/D70832

xpcom/ds/nsTArray.h

@@ -1668,7 +1668,7 @@ class nsTArray_Impl
   //
   // would accomplish the same thing as long as T has the appropriate moving
   // operator=, but some types don't for various reasons.
-  elem_type* ReconstructElementAt(index_type aIndex) {
+  elem_type* ReconstructElementAt(index_type aIndex) MOZ_NONNULL_RETURN {
     elem_type* elem = &ElementAt(aIndex);
     elem_traits::Destruct(elem);
     elem_traits::Construct(elem);