fix crash on FBSDKWebViewAppLinkResolverWebViewDelegate (#1624)

Summary:
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## Pull Request Details

It should solve this crash

#1596 (comment)

Pull Request resolved: #1624

Reviewed By: dreamolight

Differential Revision: D26103826

Pulled By: joesus

fbshipit-source-id: 3589b6b610b65e9a14506e15980aca1a8f93bd85

FBSDKCoreKit/FBSDKCoreKit/AppLink/FBSDKWebViewAppLinkResolver.m

@@ -94,13 +94,13 @@ - (void)webView:(WKWebView *)webView didFailNavigation:(WKNavigation *)navigatio
 
 - (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler
 {
-  if (self.hasLoaded) {
-    self.didFinishLoad(webView);
-    decisionHandler(WKNavigationActionPolicyCancel);
-  }
-
-  self.hasLoaded = YES;
-  decisionHandler(WKNavigationActionPolicyAllow);
+    if (self.hasLoaded) {
+        self.didFinishLoad(webView);
+        decisionHandler(WKNavigationActionPolicyCancel);
+    } else {
+        self.hasLoaded = YES;
+        decisionHandler(WKNavigationActionPolicyAllow);
+    }
 }
 
 @end