Fix NPE in DrawOverlayDetails#getSummary

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

Bug: 172381586
Test: build pass
Change-Id: I63fbeaaec6f2d0de617c6e104af341806605a6c2
diff --git a/src/com/android/settings/applications/appinfo/DrawOverlayDetails.java b/src/com/android/settings/applications/appinfo/DrawOverlayDetails.java
index 0f90c69..5f7e56f 100644
--- a/src/com/android/settings/applications/appinfo/DrawOverlayDetails.java
+++ b/src/com/android/settings/applications/appinfo/DrawOverlayDetails.java
@@ -158,6 +158,10 @@
     }
 
     public static CharSequence getSummary(Context context, AppEntry entry) {
+        if (entry == null) {
+            return "";
+        }
+
         OverlayState state;
         if (entry.extraInfo instanceof OverlayState) {
             state = (OverlayState) entry.extraInfo;