Don't try to apply nonexistent patches

If a stable release was just pushed after we triggered testing but before the pipeline executed, we get a bunch of links to nonexistent patches. Those fail to apply with "patch is empty" messages which is not exactly what we'd like. We need to check the patch exists before trying to apply it.

Since the error handling in the pipeline and reporter is messed up we can't exit 1 from the check without marking the stage as failed and spamming people that their patches are broken (which they are not). Instead, just skip the patch application and logging for now.

Signed-off-by: Veronika Kabatova vkabatov@redhat.com