Merge pull request avivais#66 from quilligana/coldstart-pn

Fix avivais#24 (android): Issue with android back button and background push notifications

Author: taivo

.DS_Store

@@ -1 +1,2 @@
 *.log
+.DS_Store

.gitignore

@@ -188,6 +188,7 @@ public void onResume(boolean multitasking) {
    public void onDestroy() {
       gWebView = null;
     	gForeground = false;
+      gEventCallback = null;
 
     	super.onDestroy();
    }