Flip inverted boolean check

Prevent nil dereference when feeds without published dates are processed

fix: clear cached content when feed URL changes

Also prepare release 0.3.8

Prepare v0.3.7

Signed-off-by: AKP <[email protected]>

Alter 2 files

Update `CHANGELOG.md`
Update `Dockerfile`

Add space for contact information in user agent

Signed-off-by: AKP <[email protected]>

Update changelog format

Signed-off-by: AKP <[email protected]>