Tableresize throws an error when hovering over table with only header rows

[f1ames]

What type of issue would you like to report?

Bug

Check if the issue is already reported

https://dev.ckeditor.com/ticket/17066

Provide detailed reproduction steps (if any)

1. Set editor config to:

config.plugins =
	'table,' +
	'tableresize,' +
	'tableselection,' +
	'toolbar,' +
	'wysiwygarea';

2. Set editor content to:

<table border="1" cellpadding="1" cellspacing="1" style="width:500px">
	<thead>
	<tr>
		<th scope="col">1</th>
		<th scope="col">2</th>
	</tr>
	</thead>
	<tbody>
	<tr>
		<td>3</td>
		<td>4</td>
	</tr>
	</tbody>
</table>

<p>Foobar</p>

3. Switch to WYSIWYG mode.
4. Select part of the table (including header) and copy.
5. Paste somewhere else.
6. Hover over pasted table.

Expected result

It is possible to resize a table (especially column by dragging inner border). No exception is thrown.

Actual result

Exception is thrown. It is not possible to resize the table.

Other details

• Browser: Chrome, FF, IE
• OS: OS X
• CKEditor version: 4.7.0
• Installed CKEditor plugins: See step 1 in repro steps

[f1ames]

It seems the cause of the issue is somewhere else. Copying selection like

[<table border="1" cellpadding="1" cellspacing="1" style="width:500px">
	<thead>
		<tr>
			<th scope="col">1</th>
			<th scope="col">2</th>
		</tr>
	</thead>
	<tbody>
		<tr>
			<td>3</td>
			<td>4</td>
		</tr>
	</tbody>
</table>]

<p>Foobar</p>

produces new table with html like:

<table border="1" cellpadding="1" cellspacing="1" style="width:500px">
	<thead>
		<tr>
			<th scope="col">1</th>
			<th scope="col">2</th>
		</tr>
		<tr>
			<td>3</td>
			<td>4</td>
		</tr>
	</thead>
</table>

It works like this only with tableselection plugin enabled.

[f1ames]

There is related issue #422. However, it is possible to reproduce the issue without tableselection plugin.

Reproduction steps

1. Set editor config to:

config.plugins =
	'table,' +
	'tableresize,' +
	'toolbar,' +
	'wysiwygarea';

2. Set editor content to (use setData):

<table border="1" cellpadding="1" cellspacing="1" style="width:500px">
	<thead>
		<tr>
			<th scope="col">1</th>
			<th scope="col">2</th>
		</tr>
	</thead>
</table>

<p>Foobar</p>

3. Hover over table.

Notice: When table with one row which is header is inserted via table plugin dialog, the empty tbody element is inserted. When such table is inserted via setData, as initial content or pasted - the empty tbody is not present.
Tableresize plugin assumes there is always tbody element which is not a valid assumption.