fix: add conditional for `srcDir` configuration

[fabio-nettis]

Description

Resolves an issue where an error would be generated due to an invalid src directory when accessing any media whatsoever.

Fixes #17

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules

[stafyniaksacha]

Hello @fabio-nettis Sorry for the delay!

I just want to know in which case those values are unset? (It shouldn't as they are core values)

If they are unset, maybe they are no public file served (maybe due to a user config?)

[fabio-nettis]

Hello @stafyniaksacha

Problematically the error appears in a extremely large project with a lot of customization, thus it is really hard to say what exactly goes into play when creating the error.

If you want I can try to create a minimal setup example and try to reproduce the error.

[fabio-nettis]

I am not able to reproduce the error with a fresh instance of Strapi. Closing for now because of missing reproducibility.