move isCombinedMode to AppBase so we wouldn't crash in preferences

js/AppBase.js

@@ -134,6 +134,9 @@ define(["dojo/_base/declare"], function (declare) {
 			}
 
 		},
+		isCombinedMode: function() {
+			return this.getInitParam("combined_display_mode");
+		},
 		getActionByHotkeySequence: function (sequence) {
 			const hotkeys_map = App.getInitParam("hotkeys");
 

js/tt-rss.js

@@ -204,9 +204,6 @@ require(["dojo/_base/kernel",
 
 					return Feeds.reloadCurrent('');
 				},
-				isCombinedMode: function() {
-					return App.getInitParam("combined_display_mode");
-				},
 				hotkeyHandler: function(event) {
 					if (event.target.nodeName == "INPUT" || event.target.nodeName == "TEXTAREA") return;