Improve capturing the legacy response

Make sure we don't leave an active output buffer behind when things
go south and an exception is thrown.

Additionally, don't try to use http_response_code() to figure out the
response status code if one has been returned from the $legacyExecutionCallback.

Author: mpdude

Integration/LegacyCaptureResponseFactory.php

@@ -28,19 +28,25 @@ class LegacyCaptureResponseFactory
     public static function create($legacyExecutionCallback)
     {
         ob_start();
-        $statusCode = call_user_func($legacyExecutionCallback) ?: 200;
+        try {
+            $statusCode = call_user_func($legacyExecutionCallback);
+            $content = ob_get_contents();
+        } finally {
+            ob_end_clean();
+        }
 
-        if (function_exists('http_response_code')) {
-            $statusCode = http_response_code();
+        if ($statusCode === null) {
+            if (function_exists('http_response_code')) {
+                $statusCode = http_response_code();
+            } else {
+                $statusCode = 200;
+            }
         }
 
         if (headers_sent()) {
             throw new LegacyIntegrationException("It must be possible to caputure the legacy application's output with ob_start(). Headers and/or output must not have been sent to the client.");
         }
 
-        $content = ob_get_contents();
-        ob_end_clean();
-
         $headers = headers_list();
         header_remove();