.html() can return null

.html() can return null when querying an element that does not exist. 

Repro:

        const response = await axios.default.get('https://www.google.com/')
        const $ = cheerio.load(response.data)
        const foo = $('.bar').html()
        console.log(`foo is: ${foo}`) //foo is: null

types/cheerio/index.d.ts

@@ -172,7 +172,7 @@ interface Cheerio {
 
     empty(): Cheerio;
 
-    html(): string;
+    html(): string | null;
     html(html: string): Cheerio;
 
     text(): string;