Ignore a keydown that carries no key

Picking a saved login from Chrome's password autofill dispatches a plain
Event named "keydown", with no key on it. The shortcut listener passed it to
comboOf, which read the key's length and threw -- an uncaught TypeError in
the console on every sign-in. Harmless, since nothing was bound to it, but
it was noise that looks like a real fault.

comboOf now returns null for an event with no key, as it already does for a
bare modifier, so the listener stops there.

web/src/lib/__tests__/keyboardKeyless.test.ts

@@ -0,0 +1,42 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { comboOf, keyboard } from "@/lib/keyboard";
+
+/*
+ * A "keydown" that carries no key. Chrome's password autofill dispatches one
+ * as a plain Event when a saved login is picked, and comboOf read `key.length`
+ * off it -- an uncaught TypeError in the console on every sign-in.
+ */
+
+let pop: (() => void) | null = null;
+
+afterEach(() => {
+  pop?.();
+  pop = null;
+});
+
+describe("a keydown with no key", () => {
+  it("has no combo", () => {
+    expect(comboOf(new Event("keydown") as KeyboardEvent)).toBeNull();
+  });
+
+  it("reaches no binding and throws nothing", () => {
+    const handler = vi.fn();
+    pop = keyboard.pushScope("test", [{ keys: "e", description: "Archive", group: "Mail", handler }]);
+    const errors: unknown[] = [];
+    const onError = (ev: ErrorEvent) => errors.push(ev.error);
+    window.addEventListener("error", onError);
+    try {
+      window.dispatchEvent(new Event("keydown", { bubbles: true }));
+    } finally {
+      window.removeEventListener("error", onError);
+    }
+    expect(errors).toEqual([]);
+    expect(handler).not.toHaveBeenCalled();
+  });
+
+  it("leaves real keys alone", () => {
+    expect(comboOf(new KeyboardEvent("keydown", { key: "e" }))).toBe("e");
+    expect(comboOf(new KeyboardEvent("keydown", { key: "E", shiftKey: true }))).toBe("E");
+    expect(comboOf(new KeyboardEvent("keydown", { key: "Enter", ctrlKey: true }))).toMatch(/enter$/);
+  });
+});

web/src/lib/keyboard.ts

@@ -136,6 +136,10 @@ const isMac = typeof navigator !== "undefined" && /Mac|iPhone|iPad/.test(navigat
 
 export function comboOf(e: KeyboardEvent): string | null {
   const key = e.key;
+  // Chrome's password autofill dispatches a plain Event named "keydown" when a
+  // saved login is picked: no key, nothing to match, and reading its length
+  // threw on every sign-in.
+  if (!key) return null;
   if (key === "Shift" || key === "Control" || key === "Alt" || key === "Meta") return null;
   const parts: string[] = [];
   const mod = isMac ? e.metaKey : e.ctrlKey;