Fix TypeError: Cannot read properties of null

Turbo expects that when there are errors in validations, for example, it should respond with status 422, which causes the iframe to disappear from the DOM, so the null error occurs in subsequent requests.

Author: sergioalcaraz

webroot/js/inject-iframe.js

@@ -77,7 +77,7 @@ if (elem) {
         url: this._arguments && this._arguments[1],
         type: this.getResponseHeader('Content-Type'),
       };
-      iframe.contentWindow.postMessage(`ajax-completed$$${JSON.stringify(params)}`, window.location.origin);
+      iframe.contentWindow?.postMessage(`ajax-completed$$${JSON.stringify(params)}`, window.location.origin);
     }
     if (original) {
       return original.apply(this, [].slice.call(arguments));
@@ -124,7 +124,7 @@ if (elem) {
             url,
             type: response.headers.get('Content-Type'),
           };
-          iframe.contentWindow.postMessage(`ajax-completed$$${JSON.stringify(params)}`, window.location.origin);
+          iframe.contentWindow?.postMessage(`ajax-completed$$${JSON.stringify(params)}`, window.location.origin);
         }
         return response;
       } catch (error) {
@@ -138,7 +138,7 @@ if (elem) {
           type: null,
           error: error.message,
         };
-        iframe.contentWindow.postMessage(`ajax-completed$$${JSON.stringify(params)}`, window.location.origin);
+        iframe.contentWindow?.postMessage(`ajax-completed$$${JSON.stringify(params)}`, window.location.origin);
         throw error;
       }
     };