[Bugfix]fix NullPointException when PackageInfo's verifiers is null

PackageInfo's verifiers will be null sometime when cancel install app, it will casue system server NPE.

Bug: 254754001
Test: MTBF

Change-Id: I1f06b4ea9610eb268cb3addcb2b44ac95520e140

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

@@ -643,7 +643,7 @@ final class VerificationParams extends HandlerParams {
 
     private List<ComponentName> matchVerifiers(PackageInfoLite pkgInfo,
             List<ResolveInfo> receivers, final PackageVerificationState verificationState) {
-        if (pkgInfo.verifiers.length == 0) {
+        if (pkgInfo.verifiers == null || pkgInfo.verifiers.length == 0) {
             return null;
         }