Handling "undefined"#39

Maybe this is by design, but I was surprised to learn that this: ``` import { merge } from "merge-anything" const defaultTheme = {} const theme = undefined merge(defaultTheme, theme) ``` Returns `undefined`. Is this expected, maybe it is, but I was kind of expecting it to return `{}`. Am I right? I would hate to have to handle this scenario like this everytime: ``` merge(defaultTheme, theme || {}) ```