Fixed #7137 by checking for Response before calling getBody() on it (#7138)

Author: fMads

modules/swagger-codegen/src/main/resources/php/api.mustache

@@ -131,7 +131,7 @@ use {{invokerPackage}}\ObjectSerializer;
                     "[{$e->getCode()}] {$e->getMessage()}",
                     $e->getCode(),
                     $e->getResponse() ? $e->getResponse()->getHeaders() : null,
-                    $e->getResponse()->getBody()->getContents()
+                    $e->getResponse() ? $e->getResponse()->getBody()->getContents() : null
                 );
             }