fix(core): dispose sets helper to null

src/lib/InstantSearch.js

@@ -339,7 +339,13 @@ class InstantSearch extends EventEmitter {
    */
   dispose() {
     this.removeWidgets(this.widgets);
+    // You can not start an instance two times, therefore a disposed instance needs to set started as false
+    // otherwise this can not be restarted at a later point.
     this.started = false;
+
+    // The helper needs to be reset to perform the next search from a fresh state.
+    // If not reset, it would use the state stored before calling `dispose()`.
+    this.helper = null;
   }
 
   createURL(params) {

src/lib/__tests__/InstantSearch-test.js

@@ -518,6 +518,27 @@ describe('InstantSearch lifecycle', () => {
   });
 });
 
+describe('dispose', () => {
+  it('should set the helper to `null`', () => {
+    const search = new InstantSearch({
+      indexName: '',
+      searchClient: { async search() {} },
+    });
+
+    search.start();
+
+    expect(search.helper).not.toBe(null);
+
+    search.dispose();
+
+    expect(search.helper).toBe(null);
+
+    search.start();
+
+    expect(search.helper).not.toBe(null);
+  });
+});
+
 it('Allows to start without widgets', () => {
   const instance = new InstantSearch({
     searchClient: {