数值步长输入组件，修复空值时显示异常的问题

Tevin

2022-01-21 eb514affa9174c7f931b3e71435e7ee819e2d4d0

 forms/numberStep/cNumberStep.scss

@@ -48,5 +48,12 @@
                color: #999;
            }
        }
        &.on-empty {
            .at-input-number {
                input {
                    color: transparent;
                }
            }
        }
    }
}