Fixes bug where match preview wouldn't get hidden if match preview was

chrome/browser/tab_contents/match_preview.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/tab_contents/match_preview.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/string_number_conversions.h"
@@ skipping 487 matching lines @@
 
   omnibox_bounds_ = bounds;
   if (preview_contents_.get() && is_showing_instant() &&
       !is_waiting_for_load()) {
     SendOmniboxBoundsScript(preview_contents_.get(),
                             GetOmniboxBoundsInTermsOfPreview());
   }
 }
 
 void MatchPreview::DestroyPreviewContents() {
+  if (!preview_contents_.get()) {
+    // We're not showing anything, nothing to do.
+    return;
+  }
+
   delegate_->HideMatchPreview();
   delete ReleasePreviewContents(false);
 }
 
 void MatchPreview::CommitCurrentPreview() {
   DCHECK(preview_contents_.get());
   delegate_->CommitMatchPreview();
 }
 
 TabContents* MatchPreview::ReleasePreviewContents(bool commit_history) {
@@ skipping 56 matching lines @@
 gfx::Rect MatchPreview::GetOmniboxBoundsInTermsOfPreview() {
   if (omnibox_bounds_.IsEmpty())
     return omnibox_bounds_;
 
   gfx::Rect preview_bounds(delegate_->GetMatchPreviewBounds());
   return gfx::Rect(omnibox_bounds_.x() - preview_bounds.x(),
                    omnibox_bounds_.y() - preview_bounds.y(),
                    omnibox_bounds_.width(),
                    omnibox_bounds_.height());
 }