Prebuilt layout import fails because of an em-dash

First of all, I want to say that I really love Page Builder and really enjoy using it. It is a very nice tool indeed!

However, I’ve noticed a strange issue: if a prebuilt layout’s cell contains an em-dash (a long dash character) it hangs when trying to apply a prebuilt layout to the page.

When this error happens, JavaScript console shows the following error:

TypeError: e is null
[7]</t.exports<.loadSelectedLayout/<()
 siteorigin-panels-24.min.js:1
bound ()
 self-hosted:756
n.Callbacks/i()
 jquery.js:2
n.Callbacks/j.fireWith()
 jquery.js:2
y()
 jquery.js:4
.send/c()

How to reproduce:
1. Insert a prebuilt layout provided below into a functions.php file.
2. Open a page in a WP page editor.
3. Switch to using a Page Builder.
4. Hit ‘Prebuilt’ button.
5. From the list of layouts choose the test one.
Then the system hangs and nothing happens.

Here is the layout that can be used to reproduce the error:

$layouts['test-page'] = array(
'name' => __('Test page', 'theme'),    // Required
'description' => __('', 'theme'),    // Optional
'widgets' =>
	array (
		0 =>
			array (
				'title' => '',
				'text' => '—

',
				'text_selected_editor' => 'tinymce',
				'autop' => true,
				'_sow_form_id' => '5768fe774e40b',
				'panels_info' =>
					array (
						'class' => 'SiteOrigin_Widget_Editor_Widget',
						'grid' => 0,
						'cell' => 0,
						'id' => 0,
						'widget_id' => 'f89cf0e3-aa98-40c9-8526-255ee63413f8',
						'style' =>
							array (
								'background_image_attachment' => false,
								'background_display' => 'tile',
							),
					),
			),
	),
'grids' =>
	array (
		0 =>
			array (
				'cells' => 1,
				'style' =>
					array (
					),
			),
	),
'grid_cells' =>
	array (
		0 =>
			array (
				'grid' => 0,
				'weight' => 1,
			),
	),
);

The text that causes the problem is an em-dash inside a ‘text’ field value. If replaced with some other character, it works just fine. So it looks like it does not like em-dash for some reason.