[builder] Fix minor bug introduced in 01d8c708b21d25ead
[builder] Makes the selection of Morsy color more robust with several instances

Accounts for Blender autorenaming Morsy material (ie, body.001,
body.002...)
[sensor] Do not crash when using cameras in fastmode

Instead, display a gentle warning.

While here, slightly improve performances of camera by skipping useless
test once the camera is setup.