Removing superfluous mensural signs

[Marcel Korpel]

Hi all,

Please have a look at http://pastebin.com/uxvQGR7y

Using `\set Staff.timeSignatureFraction = #'(2 . 2)` (lines 74 & 78,
etc.) I added repeated mensural signs (like it was in the source).
When looking at the end of bar 36, you can see that the sign is drawn
too early (and it is repeated at the beginning of bar 37).

How do I remove the extra signs at the end of bar 36?

Thank you in advance!

Marcel