ensure that messages are sent to the WV on the main thread

Author: marcuswestin

WebViewJavascriptBridge/WebViewJavascriptBridge.m

@@ -106,7 +106,13 @@ - (void)_dispatchMessage:(NSDictionary *)message {
     messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\n" withString:@"\\n"];
     messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\r" withString:@"\\r"];
     messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\f" withString:@"\\f"];
-    [_webView stringByEvaluatingJavaScriptFromString:[NSString stringWithFormat:@"WebViewJavascriptBridge._handleMessageFromObjC('%@');", messageJSON]];
+    if ([[NSThread currentThread] isMainThread]) {
+        [_webView stringByEvaluatingJavaScriptFromString:[NSString stringWithFormat:@"WebViewJavascriptBridge._handleMessageFromObjC('%@');", messageJSON]];
+    } else {
+        dispatch_sync(dispatch_get_main_queue(), ^{
+            [_webView stringByEvaluatingJavaScriptFromString:[NSString stringWithFormat:@"WebViewJavascriptBridge._handleMessageFromObjC('%@');", messageJSON]];
+        });
+    }
 }
 
 - (void)_flushMessageQueue {