test(web): #105 review — the stylesheet check no longer compares a string with undefined

`head` is always a string, so `head !== undefined` was always true and the
condition was only ever "depth 0 or 1". Said plainly now. The check behaves
as before: run alone against samples, it still fails on an unscoped rule at
the top level and inside @media, and passes the real stylesheet.

Author: ndemianc

web/test/unit/skin.test.js

@@ -71,7 +71,7 @@ test('every rule of the stylesheet is under body.lc-web', () => {
 			depth++; head = '';
 		} else if (ch === '}') { depth--; head = ''; }
 		else if (ch === ';' && depth > 0) { head = ''; }
-		else if (depth === 0 || (depth === 1 && head !== undefined)) { head += ch; }
+		else if (depth === 0 || depth === 1) { head += ch; }
 	}
 	assert.strictEqual(depth, 0, 'balanced braces');
 	assert.deepStrictEqual(bad.filter((s) => s && !/^\d/.test(s)), []);