return empty messages to avoid connection errors in Chrome

extension/ui/bg/ui-button.js

@@ -88,6 +88,7 @@ singlefile.extension.ui.bg.button = (() => {
 		if (message.method.endsWith(".processCancelled")) {
 			onCancelled(sender.tab.id, message.options);
 		}
+		return Promise.resolve({});
 	}
 
 	function onTabUpdated(tabId, changeInfo, tab) {

lib/frame-tree/bg/frame-tree.js

@@ -30,6 +30,7 @@ singlefile.lib.frameTree.bg.main = (() => {
 	browser.runtime.onMessage.addListener((message, sender) => {
 		if (message.method == "frameTree.initResponse") {
 			browser.tabs.sendMessage(sender.tab.id, message, { frameId: 0 });
+			return Promise.resolve({});
 		}
 	});
 	return {};

lib/lazy/bg/lazy-timeout.js

@@ -34,6 +34,7 @@ singlefile.lib.lazy.bg.main = (() => {
 		}
 		if (message.method == "lazyTimeout.clearTimeout") {
 			clearTimeout(message.id);
+			return Promise.resolve({});
 		}
 	});
 	return {};