[Contextual Search] Fix NPE when no Search Term.

chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchManager.java b/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchManager.java
index beaff0f6f6b3611522e0986bbf1212a934e72e8d..a8f3a97d586ab533c9d205a2d74feac902cfc58d 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchManager.java
@@ -6,6 +6,7 @@ package org.chromium.chrome.browser.contextualsearch;
 
 import android.app.Activity;
 import android.content.Context;
+import android.text.TextUtils;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.ViewTreeObserver;
@@ -731,7 +732,7 @@ public class ContextualSearchManager extends ContextualSearchObservable
             alternateTerm = null;
             doPreventPreload = true;
         }
-        if (!searchTerm.isEmpty()) {
+        if (!TextUtils.isEmpty(searchTerm)) {
             // TODO(donnd): Instead of preloading, we should prefetch (ie the URL should not
             // appear in the user's history until the user views it).  See crbug.com/406446.
             boolean shouldPreload = !doPreventPreload && mPolicy.shouldPrefetchSearchResult(true);