Avoid division by zero error when AppOps history is empty.

Test: manual verification
Bug: 143519689
Change-Id: Idbabfcede887382a29e39702d38959639f34b7c7

services/core/java/com/android/server/stats/pull/StatsPullAtomService.java

@@ -2947,7 +2947,7 @@ public class StatsPullAtomService extends SystemService {
     }
 
     int processHistoricalOps(HistoricalOps histOps, int atomTag, List<StatsEvent> pulledData) {
-        int counter = 0;
+        int counter = 1;
         for (int uidIdx = 0; uidIdx < histOps.getUidCount(); uidIdx++) {
             final HistoricalUidOps uidOps = histOps.getUidOpsAt(uidIdx);
             final int uid = uidOps.getUid();