(core): fix SLandmarks by setting an optional input for the key "matrix"
Description
Set SLandmark's matrix input optional.
The matrix input was a locked input, making any application crash once the service is called without specifying a matrix input.
With this MR we set that input as a weak input, allowing us to avoid the crash was the matrix input isn't specified.
Closes #661 (closed)
How to test it?
- Launch OgreViewer
- Load DICOM Data
- Set Landmarks with a ctrl+clicks