test: UniError constructor 增加无参数，1参数测试

uni_modules/uts-tests/utssdk/Error.uts

@@ -9,6 +9,11 @@ export function testError(): Result {
               expect((e as Error).message).toEqual("Whoops!");
             }
         })
+        
+        test('UniError', () => {
+          expect(new UniError().message).toEqual('')
+          expect(new UniError('Whoops!').message).toEqual('Whoops!')
+        })
         // test('name', () => {
         //     const e = new Error("Malformed input"); // e.name is 'Error'
         //     e.name = "ParseError";