[Autofill PCC]: Fix SaveInfo IllegalArgumentException

Don't create SaveInfo if there are no eligible autofill ids.
Test: atest CtsAutoFillServiceTestCases
Bug: 281312204

Change-Id: I5c304422dde5576d0f6408e649a420b57bb2a58e

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

@@ -1716,6 +1716,7 @@ final class Session implements RemoteFillService.FillServiceCallbacks, ViewState
                     }
                 }
             }
+            if (ids.isEmpty()) return saveInfo;
             AutofillId[] autofillIds = new AutofillId[ids.size()];
             ids.toArray(autofillIds);
             return SaveInfo.copy(saveInfo, autofillIds);