KeyDescription.parseFrom return a nullable value

Previously, parseFrom would panic if parseFrom was called on a cert that did
not have the key key description OID.

PiperOrigin-RevId: 852863153

Author: sethmoo

src/main/kotlin/Extension.kt

@@ -173,8 +173,8 @@ data class KeyDescription(
     fun parseFrom(cert: X509Certificate, logFn: (String) -> Unit = {}) =
       cert
         .getExtensionValue(OID.id)
-        .let { ASN1OctetString.getInstance(it).octets }
-        .let { parseFrom(it, logFn) }
+        ?.let { ASN1OctetString.getInstance(it).octets }
+        ?.let { parseFrom(it, logFn) }
 
     @JvmStatic
     @JvmOverloads