FIX Don't throw console error if campaigns isn't installed (#1551)

Author: GuySartorelli

client/dist/js/TinyMCE_sslink-file.js

@@ -742,7 +742,7 @@ class AssetAdmin extends Component {
       onClose: this.handleCloseFile,
       onSubmit: this.handleSubmitEditor,
       onUnpublish: this.handleUnpublish,
-      addToCampaignSchemaUrl: config.form.addToCampaignForm.schemaUrl
+      addToCampaignSchemaUrl: config.form.addToCampaignForm?.schemaUrl
     };
 
     return <EditorComponent {...editorProps} />;