SysML Exporter: Added a check for selecting no viewpoint to be extracted.
The option for export is than not given. You have to always select a valid set to have the option of export as described in the af3 help section for the SysML export.
Issue-ref: 4373 Issue-URL: #4373 (closed)
Signed-off-by: Konstantin Blaschke blaschke@fortiss.org