Steps:
1) Open Writer
2) Type 'http://libreoffice.org/'
3) Press spacebar
4) Check undo list and there will be an entry for 'Typing: " "' and 'AutoCorrect'
5) Press undo to remove the auto hyperlinking of the text
6) Press undo a second time to remove the space
7) Press enter
8) Check undo list and there will be 2 entries for 'Apply attributes' and 1 entry for 'New Paragraph'
9) Press undo once will not remove auto hyperlinking as 'New paragraph' is the first undo in the list

So the workaround is to press spacebar, undo, then enter, then remove the space from the previous row.

Version: 5.4.0.0.alpha0+
Build ID: 74ccd02eda2d6325a27266fd935aba29b3d75020
CPU threads: 2; OS: Linux 4.4; UI render: default; VCL: gtk2; 
TinderBox: Linux-rpm_deb-x86_64@70-TDF, Branch:master, Time: 2017-04-27_23:51:14
Locale: en-US (en_US.UTF-8); Calc: group