Fix null handling of getPackagesForOps

This method's "ops" argument is documented as null being an acceptable
value:

    @param ops The set of operations you are interested in, or null if
    you want all of them.

However, passing null in fact always leads to a NullPointerException,
and so the "if you want all of them" functionality is effectively
uninvocable.

This commit allows null to be passed, resulting in behavior that matches
the documentation.

Fix: 182472424
Test: atest RuntimePermissionsAppOpTrackingTest#testGetAllPackagesForAllAppOps
Change-Id: Ieba1f401aba6f5607e89fa8b932c66ddf6b73ad4

core/java/android/app/AppOpsManager.java

@@ -7563,10 +7563,15 @@ public class AppOpsManager {
     @SystemApi
     @RequiresPermission(android.Manifest.permission.GET_APP_OPS_STATS)
     public @NonNull List<AppOpsManager.PackageOps> getPackagesForOps(@Nullable String[] ops) {
-        final int opCount = ops.length;
-        final int[] opCodes = new int[opCount];
-        for (int i = 0; i < opCount; i++) {
-            opCodes[i] = sOpStrToOp.get(ops[i]);
+        final int[] opCodes;
+        if (ops != null) {
+            final int opCount = ops.length;
+            opCodes = new int[opCount];
+            for (int i = 0; i < opCount; i++) {
+                opCodes[i] = sOpStrToOp.get(ops[i]);
+            }
+        } else {
+            opCodes = null;
         }
         final List<AppOpsManager.PackageOps> result = getPackagesForOps(opCodes);
         return (result != null) ? result : Collections.emptyList();