How to reproduce:

• Make sure, the auto-selection mode in Preferences->Segmentation is activated.
• Load an image and create a segmentation
• Draw a contour
• Load another image and create a segmentation for it
• Click on the segmentation of the first image
• Draw a contour --> Offset

This behavior should actually be prevented. After clicking on the first image, the segmentation bundle should demand a reinit before enabling its tools.