Sets vulture to null to prevent crashes caused by unlinkToDeath.

Fixes: 130215863
Bug: 129250887
Test: manual verification
Change-Id: I62e8f742869967b6a4e1f56aa82f3e17ae99b16f

services/autofill/java/com/android/server/autofill/Session.java

@@ -704,6 +704,7 @@ final class Session implements RemoteFillService.FillServiceCallbacks, ViewState
             mClient.asBinder().linkToDeath(mClientVulture, 0);
         } catch (RemoteException e) {
             Slog.w(TAG, "could not set binder death listener on autofill client: " + e);
+            mClientVulture = null;
         }
     }
 
@@ -714,6 +715,7 @@ final class Session implements RemoteFillService.FillServiceCallbacks, ViewState
             if (!unlinked) {
                 Slog.w(TAG, "unlinking vulture from death failed for " + mActivityToken);
             }
+            mClientVulture = null;
         }
     }