Feed list sometimes can't fetch new feeds when scrolling down in Firefox

[stbinan]

Solution:
in js/FeedList.coffee:
change

 	checkScroll: =>
		if document.body.scrollTop + window.innerHeight > document.getElementById("FeedList").clientHeight - 400 and not @updating and @feeds?.length > 5 and Page.mode == "Sites" and @limit < 300

to

 	checkScroll: =>
        scrollTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop || 0
		if scrollTop + window.innerHeight > document.getElementById("FeedList").clientHeight - 400 and not @updating and @feeds?.length > 5 and Page.mode == "Sites" and @limit < 300

Reference: https://stackoverflow.com/questions/28633221/document-body-scrolltop-firefox-returns-0-only-js

[HelloZeroNet]

Thanks: Fixed 8a08df4