Null check inside filterIfNotSystemUser

List<ResolveInfo> is defined as nullable, so if that ever happens,
need to handle it in the filter method.

Bug: 222180729

Test: presubmit

Change-Id: I84e8b66485f226e0d01074e01c77fa0b71f37122

services/core/java/com/android/server/pm/ComputerEngine.java

@@ -1431,7 +1431,8 @@ public class ComputerEngine implements Computer {
         if (userId == UserHandle.USER_SYSTEM) {
             return resolveInfos;
         }
-        for (int i = resolveInfos.size() - 1; i >= 0; i--) {
+
+        for (int i = CollectionUtils.size(resolveInfos) - 1; i >= 0; i--) {
             ResolveInfo info = resolveInfos.get(i);
             if ((info.activityInfo.flags & ActivityInfo.FLAG_SYSTEM_USER_ONLY) != 0) {
                 resolveInfos.remove(i);