Add a missing null check

Test: manual

bug::62755026

Change-Id: Icf719d0e62986febd4d31f22be3e59d83c8e6e09
(cherry picked from commit 0ae9570c9925603a04d5a78775a68cc9d437542b)
diff --git a/services/core/java/com/android/server/pm/PackageManagerService.java b/services/core/java/com/android/server/pm/PackageManagerService.java
index ddb5832..f36b762 100644
--- a/services/core/java/com/android/server/pm/PackageManagerService.java
+++ b/services/core/java/com/android/server/pm/PackageManagerService.java
@@ -4004,6 +4004,9 @@
         // reader
         synchronized (mPackages) {
             final BasePermission p = mSettings.mPermissions.get(name);
+            if (p == null) {
+                return null;
+            }
             // If the caller is an app that targets pre 26 SDK drop protection flags.
             final PermissionInfo permissionInfo = generatePermissionInfo(p, flags);
             if (permissionInfo != null) {