Ensure that correct error messages show up in the Edit user modal (#48966)

e2e/test/scenarios/admin-2/people.cy.spec.js

@@ -255,9 +255,17 @@ describe("scenarios > admin > people", () => {
       showUserOptions(normalUserName);
       // eslint-disable-next-line no-unscoped-text-selectors -- deprecated usage
       cy.findByText("Edit user").click();
-      cy.findByDisplayValue(normal.first_name).click().clear().type(NEW_NAME);
 
-      clickButton("Update");
+      modal().within(() => {
+        cy.log("Should display error messages (metabase#46449)");
+        cy.findByLabelText("First name").click().clear().type(" ");
+        clickButton("Update");
+        cy.findByText(/non-blank string./).should("exist");
+
+        cy.findByLabelText("First name").click().clear().type(NEW_NAME);
+        clickButton("Update", { timeout: 4000 });
+      });
+
       // eslint-disable-next-line no-unscoped-text-selectors -- deprecated usage
       cy.findByText(NEW_FULL_NAME);
       cy.location().should(loc => expect(loc.pathname).to.eq("/admin/people"));
@@ -872,8 +880,8 @@ function showUserOptions(full_name) {
     });
 }
 
-function clickButton(button_name) {
-  cy.button(button_name).should("not.be.disabled").click();
+function clickButton(button_name, opts = {}) {
+  cy.button(button_name, opts).should("not.be.disabled").click();
 }
 
 function assertTableRowsCount(length) {

frontend/src/metabase/redux/user.ts

@@ -43,7 +43,8 @@ export const currentUser = createReducer<User | null>(null, builder => {
       return state;
     })
     .addCase(Users.actionTypes.UPDATE, (state, { payload }) => {
-      const isCurrentUserUpdated = state?.id === payload.user.id;
+      const isCurrentUserUpdated =
+        payload.user && state?.id === payload.user.id;
       if (isCurrentUserUpdated) {
         return {
           ...state,