Even this is not the common bugs but some people might face with empty repo on Cydia after jailbreaking their iDevices. This should not be a big problem since it can be solved with simple solution. You don’t need to jailbreak the device again.
I also have faced the problem but simple can solve with restart the phone then go to Cydia, in “Changes” tab click on “Refresh”. Wait for the loading which will take times.
After that you will be able to find your repo source on Cydia is no longer empty.
Note: If you still face empty Repo on Cydia, you might need to wait a few days since it usually happens with newly jailbreak device.