Fix issue where can't long click page indicators (issue 11136731)

Change-Id: Idcd3a3eabed9db6f1ab17891544578170b8cac6f
diff --git a/src/com/android/launcher3/Workspace.java b/src/com/android/launcher3/Workspace.java
index bbe0946..66d4410 100644
--- a/src/com/android/launcher3/Workspace.java
+++ b/src/com/android/launcher3/Workspace.java
@@ -53,6 +53,7 @@
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewGroup;
+import android.view.View.OnClickListener;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityManager;
 import android.view.accessibility.AccessibilityNodeInfo;
@@ -1524,7 +1525,10 @@
         if (getPageIndicator() != null) {
             // In case accessibility state has changed, we need to perform this on every
             // attach to window
-            getPageIndicator().setOnClickListener(getPageIndicatorClickListener());
+            OnClickListener listener = getPageIndicatorClickListener();
+            if (listener != null) {
+                getPageIndicator().setOnClickListener(listener);
+            }
         }
         AccessibilityManager am = (AccessibilityManager)
                 getContext().getSystemService(Context.ACCESSIBILITY_SERVICE);