null check jarfile before using

Bug: 29937423
Change-Id: I14f8530523bedf6c287a7f89d3e54919d98454c9
diff --git a/services/core/java/com/android/server/pm/PackageManagerService.java b/services/core/java/com/android/server/pm/PackageManagerService.java
index a30422d..c3a8e50 100644
--- a/services/core/java/com/android/server/pm/PackageManagerService.java
+++ b/services/core/java/com/android/server/pm/PackageManagerService.java
@@ -7986,7 +7986,9 @@
         } catch (IOException ignore) {
         } finally {
             try {
-                jarFile.close();
+                if (jarFile != null) {
+                    jarFile.close();
+                }
             } catch (IOException ignore) {}
         }
         return false;