Trying to resolve runtime error -.-

2014-07-02 19:52:41.041 Speaker[5701:303] Unknown class
'SpeakerDelegate', using 'NSObject' instead. Encountered in Interface
Builder file at path
/Users/livio/Library/Developer/Xcode/DerivedData/Speaker-dwbnojitzbkhgqe
zrivyfmszniyy/Build/Products/Debug/Speaker.app/Contents/Resources/Base.l
proj/MainMenu.nib.