Fix NPE in NewReturnToCallController.createLettleTileDrawable().

After searching contact info, the associated dialer call object might be removed from CallList, which causes NPE.

Test: NewReturnToCallControllerTest
PiperOrigin-RevId: 181387022
Change-Id: Icabaeccc96e039c8ac53d66c23af89d3eb0823a9
diff --git a/java/com/android/incallui/NewReturnToCallController.java b/java/com/android/incallui/NewReturnToCallController.java
index ca60a52..b8798b1 100644
--- a/java/com/android/incallui/NewReturnToCallController.java
+++ b/java/com/android/incallui/NewReturnToCallController.java
@@ -318,8 +318,10 @@
         newReturnToCallController.onPhotoAvatarReceived(entry.photo);
       } else {
         DialerCall dialerCall = CallList.getInstance().getCallById(callId);
-        newReturnToCallController.onLetterTileAvatarReceived(
-            newReturnToCallController.createLettleTileDrawable(dialerCall, entry));
+        if (dialerCall != null) {
+          newReturnToCallController.onLetterTileAvatarReceived(
+              newReturnToCallController.createLettleTileDrawable(dialerCall, entry));
+        }
       }
     }
 
@@ -334,8 +336,10 @@
         newReturnToCallController.onPhotoAvatarReceived(entry.photo);
       } else {
         DialerCall dialerCall = CallList.getInstance().getCallById(callId);
-        newReturnToCallController.onLetterTileAvatarReceived(
-            newReturnToCallController.createLettleTileDrawable(dialerCall, entry));
+        if (dialerCall != null) {
+          newReturnToCallController.onLetterTileAvatarReceived(
+              newReturnToCallController.createLettleTileDrawable(dialerCall, entry));
+        }
       }
     }
   }