Merging Mono failed when creating installer for osx

Question

I get the following error when I try to publish my MonoMac application as mac installer. I am using MonoDevelop 2.4.2, MonoMac 2.4.2.4 and the project is a fresh project created by the "C# MonoMac Project".

I just added two classes and called them via Initialize of the MainWindow.

Creating app bundle
Contents/Info.plist
Contents/PkgInfo
Contents/Resources/MainMenu.nib
Contents/Resources/MainWindow.nib
Contents/Resources/Scripts/itunes.scpt
Contents/Resources/Scripts/out.txt

Merging Mono into app bundle
mmp --linksdkonly -o "/tmp/monomac-build-634406615434742750" -n "djBillboard" -a "/Library/Frameworks/Mono.framework/Versions/2.10.1/lib/mono/4.0/System.dll" -a "/Library/Frameworks/Mono.framework/Versions/2.10.1/lib/mono/4.0/System.Xml.dll" -a "/Library/Frameworks/Mono.framework/Versions/2.10.1/lib/mono/4.0/System.Core.dll" -a "/Library/Frameworks/Mono.framework/Versions/2.10.1/lib/mono/4.0/System.Xml.Linq.dll" -a "/Library/Frameworks/Mono.framework/Versions/2.10.1/lib/mono/4.0/System.Drawing.dll" -a "/Users/Sebi/.config/MonoDevelop/addins/MonoDevelop.MonoMac.2.4.2.4/MonoMac.dll" -a "/Users/Sebi/Projects/djBillboard/lib/Nugget.dll" "/Users/Sebi/Projects/djBillboard/djBillboard/bin/Debug/djBillboard.exe"

Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object
  at MonoMac.Bundler.Driver.Link () [0x00000] in :0 
  at MonoMac.Bundler.Driver.Main (System.String[] args) [0x00000] in :0 

Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object
  at MonoMac.Bundler.Driver.Link () [0x00000] in :0 
  at MonoMac.Bundler.Driver.Main (System.String[] args) [0x00000] in :0 


Merging Mono failed