Fix NPE in DrawOverlayDetails#getSummary

When AppEntry is null (APP uninstalled), returns
an empty summary string.

Bug: 172381586
Test: build pass
Change-Id: I63fbeaaec6f2d0de617c6e104af341806605a6c2

src/com/android/settings/applications/appinfo/DrawOverlayDetails.java

@@ -158,6 +158,10 @@ public class DrawOverlayDetails extends AppInfoWithHeader implements OnPreferenc
     }
 
     public static CharSequence getSummary(Context context, AppEntry entry) {
+        if (entry == null) {
+            return "";
+        }
+
         OverlayState state;
         if (entry.extraInfo instanceof OverlayState) {
             state = (OverlayState) entry.extraInfo;