Should check TSFBridge availability before accessing it.

We should check whether |TSFBridge| is initialized before accessing it
in |InputMethodWinTSF::OnWillChangeFocusedClient|.

Bug: 1126159
Change-Id: If84b28007549c38e33ae947ac7d9dbec627a1ee2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2399454Reviewed-by: Yohei Yukawa <yukawa@chromium.org>
Commit-Queue: Siye Liu <siliu@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#807094}

ui/base/ime/win/input_method_win_tsf.cc

@@ -142,7 +142,7 @@ bool InputMethodWinTSF::IsCandidatePopupOpen() const {
 void InputMethodWinTSF::OnWillChangeFocusedClient(
     TextInputClient* focused_before,
     TextInputClient* focused) {
-  if (IsWindowFocused(focused_before)) {
+  if (ui::TSFBridge::GetInstance() && IsWindowFocused(focused_before)) {
     ConfirmCompositionText();
     ui::TSFBridge::GetInstance()->RemoveFocusedClient(focused_before);
   }