Add a warning for a case where user has not defined lanes and started image analysis
Right now we have rather cryptic warning message displayed in the case where
- User has added new gel
- Without defining lanes, user added new image
- After opening an image and correcting background, user gets a warning "Couldn't find entity in Gel images" in the status bar
- It is impossible to continue the analysis as lanes are not defined. As a result, buttons for lane addition in image analysis toolbar are disabled.
Case: https://forum.image.sc/t/iocbio-gel-new-open-source-gel-analysis-software/80007/3