Bug 1800404 - Make IMEStateManager::OnChangeFocusInternal stop warn…

…ing in the case that `aPresContext` is `nullptr` r=m_kato

It may be called with `nullptr` for both `aPresContent` and `aElement`.
Therefore, it should not warn it when `aPresContext` is `nullptr`.

Differential Revision: https://phabricator.services.mozilla.com/D161979

dom/events/IMEStateManager.cpp

@@ -497,12 +497,15 @@ nsresult IMEStateManager::OnChangeFocusInternal(nsPresContext* aPresContext,
 
   // If new aPresShell has been destroyed, this should handle the focus change
   // as nobody is getting focus.
-  if (NS_WARN_IF(!CanHandleWith(aPresContext))) {
+  MOZ_ASSERT_IF(!aPresContext, !aElement);
+  if (NS_WARN_IF(aPresContext && !CanHandleWith(aPresContext))) {
     MOZ_LOG(sISMLog, LogLevel::Warning,
             ("  OnChangeFocusInternal(), called with destroyed PresShell, "
              "handling this call as nobody getting focus"));
     aPresContext = nullptr;
     aElement = nullptr;
+  } else if (!aPresContext) {
+    aElement = nullptr;
   }
 
   const nsCOMPtr<nsIWidget> oldWidget = sTextInputHandlingWidget;