Mission planner exit bug?

Mission Planner 1.3.58, shows the following window when I click on “X”(exit):
"Okease Yodate - Some older library dlls are causing problems.
Could not load type “AltitudeAngelWings.ServiceLOcator” from assembly “AltitudeAngleWings,
Version = 1.0.0.0, Culture=neutral,PublicKeyToken=Null”

I just updated to MP1.3.58. Did not have this problem with previous version.