SecTrust object now is conditionally unwrapped

[giullo]

This PR fixes an issue introduced by dbeb119#diff-b9ab27dc605d36ce558013387d2ba2d5

Now the SecTrust object is conditionally unwrapped and if not found , the pinning will fail*. I was never able to reproduce the scenario where the SecTrust object is null within a wss/https connection, i think this could be related to a failed SSL handshake (maybe due to networking issues) but these are just speculations at this point.

• I consider the pinning failed, because if you end up in that code branch it's because:

1. the url is either wss or https
2. a security object was provided to perform the certificate pinning
   the client is clearly signalling is will for the pinning to be performed, so in absence of a trust that contains the certificates to be checked, i think it's better to reject the connection

[daltoniam]

Great work and thanks for fixing that issue!

[giullo]

Hey thanks for the quick approval. i see that this is included in 2.1.0, but somehow the spec hasn't been pushed to cocoa pods , because the latest available is still 2.0.4 (and if you try to target directly 2.1.0 you will get an error that the dependency can't be satisfied)

Could you have a look? ah and btw, many thanks for the great library :)

[daltoniam]

Finally got it done. Had a fair amount of trouble with CocoaPods & SPM working together. Anyway, 2.1.0 has been released!