return values

src/extension/core/bg/editor.js

@@ -81,6 +81,7 @@ async function onMessage(message, sender) {
 				await browser.tabs.sendMessage(tab.id, message);
 			}
 		}
+		return {};
 	}
 	if (message.method.endsWith(".open")) {
 		let contents;
@@ -103,5 +104,6 @@ async function onMessage(message, sender) {
 			await browser.tabs.update(tab.id, updateTabProperties);
 			tabsData.set(tab.id, { url: tab.url, content: contents.join(""), filename: message.filename });
 		}
+		return {};
 	}
 }