Fixed whitespace toggle not showing the correct diff

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/211585

app/assets/javascripts/diffs/store/mutations.js

@@ -326,6 +326,7 @@ export default {
   },
   [types.SET_SHOW_WHITESPACE](state, showWhitespace) {
     state.showWhitespace = showWhitespace;
+    state.diffFiles = [];
   },
   [types.TOGGLE_FILE_FINDER_VISIBLE](state, visible) {
     state.fileFinderVisible = visible;

changelogs/unreleased/ph-211585-fixWhitespaceToggleNotShowingCorrectDiff.yml

+---
+title: Fixed whitespace toggle not showing the correct diff
+merge_request:
+author:
+type: fixed

spec/frontend/diffs/store/mutations_spec.js

@@ -796,11 +796,13 @@ describe('DiffsStoreMutations', () => {
     it('sets showWhitespace', () => {
       const state = {
         showWhitespace: true,
+        diffFiles: ['test'],
       };
 
       mutations[types.SET_SHOW_WHITESPACE](state, false);
 
       expect(state.showWhitespace).toBe(false);
+      expect(state.diffFiles).toEqual([]);
     });
   });