Fix a NULL pointer access bug in TSFTextStore

ui/base/ime/win/tsf_text_store.cc

Index: ui/base/ime/win/tsf_text_store.cc
diff --git a/ui/base/ime/win/tsf_text_store.cc b/ui/base/ime/win/tsf_text_store.cc
index ce566890b3f8fc5c6099dc5b09219f0c2ad6e3f5..c6f9f53b70f4f4d66a907850d7382dabe56de0d4 100644
--- a/ui/base/ime/win/tsf_text_store.cc
+++ b/ui/base/ime/win/tsf_text_store.cc
@@ -585,6 +585,8 @@ STDMETHODIMP TSFTextStore::RequestSupportedAttrs(
     const TS_ATTRID* attribute_buffer) {
   if (!attribute_buffer)
     return E_INVALIDARG;
+  if (!text_input_client_)
+    return E_FAIL;
   // We support only input scope attribute.
   for (size_t i = 0; i < attribute_buffer_size; ++i) {
     if (IsEqualGUID(GUID_PROP_INPUTSCOPE, attribute_buffer[i]))
@@ -601,6 +603,8 @@ STDMETHODIMP TSFTextStore::RetrieveRequestedAttrs(
     return E_INVALIDARG;
   if (!attribute_buffer)
     return E_INVALIDARG;
+  if (!text_input_client_)
+    return E_UNEXPECTED;
   // We support only input scope attribute.
   *attribute_buffer_copied = 0;
   if (attribute_buffer_size == 0)