Check for null ApplicationInfo object in SMS.

Bug: 149448096
Test: builds
Change-Id: I783c35323ecb82721b47c1d97e211b93a2ec0d48

services/core/java/com/android/server/StorageManagerService.java

@@ -3973,7 +3973,7 @@ class StorageManagerService extends IStorageManager.Stub
             if (mIsFuseEnabled && hasMtp) {
                 ApplicationInfo ai = mIPackageManager.getApplicationInfo(packageName,
                         0, UserHandle.getUserId(uid));
-                if (ai.isSignedWithPlatformKey()) {
+                if (ai != null && ai.isSignedWithPlatformKey()) {
                     // Platform processes hosting the MTP server should be able to write in Android/
                     return Zygote.MOUNT_EXTERNAL_ANDROID_WRITABLE;
                 }