fixed issue #128 (button was disabled after loading a page on Waterfox)

extension/core/bg/tabs.js

@@ -41,6 +41,7 @@ singlefile.tabs = (() => {
 	function onTabUpdated(tabId, changeInfo, tab) {
 		singlefile.autosave.onTabUpdated(tabId, changeInfo, tab);
 		singlefile.ui.menu.onTabUpdated(tabId, changeInfo, tab);
+		singlefile.ui.button.onTabUpdated(tabId, changeInfo, tab);
 	}
 
 	function onTabRemoved(tabId) {