Make sure to not call getTelephonyManager with null context

Bug: 9465444

Change-Id: Ibe7f463da5ba0a5276701fa10ce01c28a5d4b16d
diff --git a/src/com/android/dialer/dialpad/DialpadFragment.java b/src/com/android/dialer/dialpad/DialpadFragment.java
index 3052c67..12050a1 100644
--- a/src/com/android/dialer/dialpad/DialpadFragment.java
+++ b/src/com/android/dialer/dialpad/DialpadFragment.java
@@ -1660,6 +1660,10 @@
                             // TODO: Filter out emergency numbers if
                             // the carrier does not want redial for
                             // these.
+                            // If the fragment has already been detached since the last time
+                            // we called queryLastOutgoingCall in onResume there is no point
+                            // doing anything here.
+                            if (getActivity() == null) return;
                             mLastNumberDialed = number;
                             updateDialAndDeleteButtonEnabledState();
                         }