Firefox infinate loading display on mail screen

[johndoh]

Revently I have noticed strange behavior when using Roundcube on my dev server. On the mail screen Firefox reports the page is loading forever (the X stop icon never changes to the Reload icon and the "Read [url]" message in the bottom left persists).
The browser console reports all resouces are loaded correctly. No JS errors, warnings:

Request to access cookie or storage on “[url]/program/resources/dummy.pdf” was blocked because we are blocking all third-party storage access requests and content blocking is enabled.

This issue does not effect the usability of the Roundcube interface.

The causes appears to be line 10134:

roundcubemail/program/js/app.js

Lines 10126 to 10137 in 2f64314

	window.setTimeout(function() {
	$('<object>').attr({
	data: ref.assets_path('program/resources/dummy.pdf'),
	type: 'application/pdf',
	style: 'position: "absolute"; top: -1000px; height: 1px; width: 1px'
	})
	.on('load error', function(e) {
	ref.env.browser_capabilities.pdf = e.type == 'load' ? 1 : 0;
	$(this).remove();
	})
	.appendTo(document.body);
	}, 10);

It seems like Firefox is getting confused by an element being added and removed from the DOM so quickly as adding a short delay before attempting to remove the dummy PDF object solves the issue, Firefox shows loading complete.

Tested with against 2 different webservers via HTTP and HTTPS connections.

Roundcube: git-master
Plugins: none
Skins: Elastic, Larry, Classic
Firefox 89.0.2
Windows 10

[alecpl]

Fixed.