There is no connected camera message with built in FaceTime camera
From osxdaily:


Quit all open apps that may try to use the FaceTime camera
Open Terminal, found in the /Applications/Utilities directory in OS X
Enter the following command string exactly, then hit return:

sudo killall VDCAssistant

Enter the administrator password when requested, this is required to execute a command with superuser privileges as prefixed by sudo
Relaunch the app that was attempting to use the camera


Or... Use Activity Monitor, search for VDC and force quit it.