am 2caf31a9: Fix memory leak in FragmentManager backstack.

* commit '2caf31a93708d7c27a8dc80ace3fc7c3330b2bf0':
  Fix memory leak in FragmentManager backstack.
diff --git a/src/com/android/mail/ui/OnePaneController.java b/src/com/android/mail/ui/OnePaneController.java
index 8ce5c0c..57f6d36 100644
--- a/src/com/android/mail/ui/OnePaneController.java
+++ b/src/com/android/mail/ui/OnePaneController.java
@@ -219,7 +219,6 @@
         }
         final FragmentManager fm = mActivity.getFragmentManager();
         final FragmentTransaction ft = fm.beginTransaction();
-        ft.addToBackStack(null);
         // Switching to conversation view is an incongruous transition:
         // we are not replacing a fragment with another fragment as
         // usual. Instead, reveal the heretofore inert conversation