Inspect session store on serial queue

// FREEBIE

src/Messages/TSMessagesManager.m

@@ -234,7 +234,7 @@ NS_ASSUME_NONNULL_BEGIN
         TSStorageManager *storageManager = [TSStorageManager sharedManager];
         NSString *recipientId = messageEnvelope.source;
         int deviceId = messageEnvelope.sourceDevice;
-
+        dispatch_async([OWSDispatch sessionStoreQueue], ^{
             if (![storageManager containsSession:recipientId deviceId:deviceId]) {
                 [self.dbConnection readWriteWithBlock:^(YapDatabaseReadWriteTransaction *transaction) {
                     TSErrorMessage *errorMessage =
@@ -245,13 +245,13 @@ NS_ASSUME_NONNULL_BEGIN
             }
 
             // DEPRECATED - Remove after all clients have been upgraded.
-        NSData *encryptedData = messageEnvelope.hasContent ? messageEnvelope.content : messageEnvelope.legacyMessage;
+            NSData *encryptedData
+                = messageEnvelope.hasContent ? messageEnvelope.content : messageEnvelope.legacyMessage;
             if (!encryptedData) {
                 DDLogError(@"Skipping message envelope which had no encrypted data");
                 return;
             }
 
-        dispatch_async([OWSDispatch sessionStoreQueue], ^{
             NSData *plaintextData;
 
             @try {