Fix lobby filter reset persistence

ui/lobby/src/filter.ts

@@ -33,9 +33,10 @@ export default class Filter {
     };
   };
 
-  save = (form: HTMLFormElement) => {
-    const lines = toFormLines(form);
-    this.store.set(lines);
+  save = (form: HTMLFormElement | null) => {
+    const lines = form && toFormLines(form);
+    if (lines) this.store.set(lines);
+    else this.store.remove();
     this.set(lines);
     this.root.onSetFilter();
   };

ui/lobby/src/form.ts

@@ -7,6 +7,7 @@ export interface FormObject {
 export interface FormStore {
   get: () => FormLines | null;
   set: (lines: FormLines) => void;
+  remove: () => void;
 }
 
 export const toFormLines = (form: HTMLFormElement): FormLines =>
@@ -24,4 +25,5 @@ export const toFormObject = (lines: FormLines): FormObject =>
 export const makeStore = (storage: LichessStorage): FormStore => ({
   get: () => JSON.parse(storage.get() || 'null') as FormLines,
   set: lines => storage.set(JSON.stringify(lines)),
+  remove: () => storage.remove(),
 });

ui/lobby/src/view/realTime/filter.ts

@@ -27,7 +27,7 @@ function initialize(ctrl: LobbyController, el: HTMLElement) {
     .find('form')
     .on('reset', (e: Event) => {
       e.preventDefault();
-      ctrl.filter.set(null);
+      ctrl.filter.save(null);
       ctrl.filter.open = false;
       ctrl.redraw();
     })