Hi there,
When no start date is selected, what is the type of self.start_date
just before you pass it to get_specific_rows
?
I’ve done a little mock up app that does what you are describing (I think) and things work as expected:
https://anvil.works/build#clone:BMC6UMJ46PZXGL6I=FDVGTAEQIIHLBDKC76WSLHWT
Hopefully this will help you identify the issue.
If you are able, please share a small working example app that demonstrates the issue. This can often help folks here to more easily provide assistance.