fix potential deadlock

// FREEBIE

Signal/src/environment/Migrations/OWS102MoveLoggingPreferenceToUserDefaults.m

@@ -1,5 +1,5 @@
 //
-//  Copyright © 2017 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
 //
 
 #import "OWS102MoveLoggingPreferenceToUserDefaults.h"
@@ -22,7 +22,7 @@ static NSString *const OWS102MoveLoggingPreferenceToUserDefaultsMigrationId = @"
     DDLogWarn(@"[OWS102MoveLoggingPreferenceToUserDefaultsMigrationId] copying existing logging preference to "
               @"NSUserDefaults");
 
-    NSNumber *existingValue = [self.storageManager objectForKey:PropertyListPreferencesKeyEnableDebugLog
+    NSNumber *existingValue = [transaction objectForKey:PropertyListPreferencesKeyEnableDebugLog
                                            inCollection:PropertyListPreferencesSignalDatabaseCollection];
 
     if (existingValue) {