hashcat recovers null results
I was hoping someone can explain hashcat behaviour.

I have bunch of hashes (sha512($pass.$salt)) which I run against dictionary and hashcat recovers them as null. They can be different hashes with different salts, but hashcat still recovers them as null.

Basically, output looks like [hash]:[salt]:      ...and then nothing.

Am I missing out something?
Just to be really really sure, if you do sha512($salt) on for example https://passwordsgenerator.net/sha512-hash-generator/ you don't get the hash in your output?
Yes, it does actually. What would that mean?
That hashcat is correctly showing the results. There is no password for those hashes you have, only a salt. Depending on your source this might be logical.
Makes sense, thank you, Daniel.
Although I don't fully understand, why there will need to be salt if no password?

I believe this is something to do with 'Windows Authentication' when users authenticate using Windows logon. But again why unique salt needed to be generated and as a password used encoded salt?!