Fix crash in GeolocationController when the page gets destroyed

Source/modules/geolocation/GeolocationController.cpp

Index: Source/modules/geolocation/GeolocationController.cpp
diff --git a/Source/modules/geolocation/GeolocationController.cpp b/Source/modules/geolocation/GeolocationController.cpp
index 1956eec6345fe9529451a4a5ae5c6e66895f6776..7c80533571d6fa4718d5f0ab4e8bd281191344be 100644
--- a/Source/modules/geolocation/GeolocationController.cpp
+++ b/Source/modules/geolocation/GeolocationController.cpp
@@ -64,7 +64,7 @@ void GeolocationController::addObserver(Geolocation* observer, bool enableHighAc
     if (m_client) {
         if (enableHighAccuracy)
             m_client->setEnableHighAccuracy(true);
-        if (wasEmpty && page()->visibilityState() == PageVisibilityStateVisible)
+        if (wasEmpty && page() && page()->visibilityState() == PageVisibilityStateVisible)
             m_client->startUpdating();
     }
 }
@@ -135,7 +135,7 @@ void GeolocationController::pageVisibilityChanged()
     if (m_observers.isEmpty() || !m_client)
         return;
 
-    if (page()->visibilityState() == PageVisibilityStateVisible)
+    if (page() && page()->visibilityState() == PageVisibilityStateVisible)

[adamk, 2013/10/23 15:34:38]

I'd hope that page() couldn't be null here, since this callback should be coming
from an instance of Page, but checking it is harmless enough.

         m_client->startUpdating();
     else
         m_client->stopUpdating();