Editor empty value contains formattings

[ssi-hu-tasi-norbert]

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[ x] bug report => Search github for a similar issue or PR before submitting
[ ] feature request => Please check if request is not on the roadmap already https://github.com/primefaces/primeng/wiki/Roadmap
[ ] support request => Please do not submit support request here, instead see http://forum.primefaces.org/viewforum.php?f=35

Current behavior

1. type something into an empty editor
2. choose formatting like bold. Don't type anything
3. delete back the typed content

the value is: <p><strong><span class="ql-cursor"></span></strong></p>

Expected behavior

Value should be null.

Suggestion:
let text = this.quill.getText().trim();
if (!text) {
html = null;
}

Many Thanks!

Minimal reproduction of the problem with instructions

What is the motivation / use case for changing the behavior?

Please tell us about your environment:

• Angular version: 5.2.0

• PrimeNG version: 5.0.2

• Browser: [all | Chrome XX | Firefox XX | IE XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari | iOS XX UIWebView | iOS XX WKWebView ]

• Language: [all | TypeScript X.X | ES6/7 | ES5]

• Node (for AoT issues): node --version =