clear "reply/editing/forwarding state when switching topics

src/views/messages-view.jsx

@@ -303,6 +303,8 @@ class MessagesView extends React.Component {
         scrollPosition: 0,
         fetchingMessages: false,
         showGoToLastButton: false,
+        forwardMessage: null,
+        reply: null,
         contentToEdit: null,
         dragging: false
       };

umd/index.dev.js

@@ -5721,6 +5721,8 @@ class MessagesView extends (react__WEBPACK_IMPORTED_MODULE_0___default().Compone
         scrollPosition: 0,
         fetchingMessages: false,
         showGoToLastButton: false,
+        forwardMessage: null,
+        reply: null,
         contentToEdit: null,
         dragging: false
       };