GUI displays unintentional line breaks and lines in commit messages

Summary

GUI displays unintentional line breaks and lines in commit messages.

Steps to reproduce

Create a new commit with the following message:

header

Signed-off-by: firstname lastname <lastname@domain.com>
Merge-Request: #1234 : Here comes more text in this line
Reviewed-by:  firstname lastname <lastname@domain.com>

What is the current bug behavior?

After the link for #1234, a line break is inserted and a new line is inserted:

header

Signed-off-by: firstname lastname <lastname@domain.com>
Pull-Request: #1234

 : Here comes more text in this line
Reviewed-by:  firstname lastname <lastname@domain.com>

What is the expected correct behavior?

All lines of the commit message should be formatted as in the original commit message. No line breaks should be added. No extra lines should be inserted.

This does not only apply to issue links, but has also been detected for links generated by "Custom Issue Tracker" and links inserted for simple URLs in commit messages. In all cases, a line break and a blank line are inserted.