[GHS] Error when pasting content with tabs from Google Docs

[FilipTokarski]

📝 Provide detailed reproduction steps (if any)

1. Open a google doc document
2. Type foo, press tab, type bar
3. Select this content
4. Paste into editor which has GHS options:

htmlSupport: {
	allow: [
		{
			name: /.*/,
			attributes: true,
			classes: true
		}
	]
}

✔️ Expected result

Content is pasted, no errors.

❌ Actual result

Content is not pasted. Errors in the console:

Uncaught TypeError: target[key] is not iterable
    at mergeViewElementAttributes (conversionutils.js:48)
    at UpcastDispatcher.dispatcher.on.priority (converters.js:104)
    at UpcastDispatcher.fire (emittermixin.js:199)
    at UpcastDispatcher._convertItem (upcastdispatcher.js:249)
    at UpcastDispatcher._convertChildren (upcastdispatcher.js:282)
    at UpcastDispatcher.dispatcher.on.priority (converters.js:95)
    at UpcastDispatcher.fire (emittermixin.js:199)
    at UpcastDispatcher._convertItem (upcastdispatcher.js:249)
    at UpcastDispatcher._convertChildren (upcastdispatcher.js:282)
    at UpcastDispatcher.<anonymous> (upcasthelpers.js:439)

Clipboard content:

<meta charset='utf-8'><meta charset="utf-8"><b style="font-weight:normal;" id="docs-internal-guid-a8b55294-7fff-ceb1-1e3f-df64b7c7ec04"><span style="font-size:11pt;font-family:Arial;color:#000000;background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">foo</span><span style="font-size:11pt;font-family:Arial;color:#000000;background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;"><span class="Apple-tab-span" style="white-space:pre;"> </span></span><span style="font-size:11pt;font-family:Arial;color:#000000;background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">bar</span></b>

---

If you'd like to see this fixed sooner, add a 👍 reaction to this post.

[FilipTokarski]

It's a duplicate of #10657, closing.