Use the stored error value

This resolves a static analysis warning about the value stored to `error` never being read, and following uses seem to indicate this individual case might be a typo.

peertalk/PTChannel.m

@@ -229,7 +229,7 @@ - (void)connectToPort:(in_port_t)port IPv4Address:(in_addr_t)address callback:(v
   if (fd == -1) {
     perror("socket(AF_INET, SOCK_STREAM, 0) failed");
     error = errno;
-    if (callback) callback([[NSError alloc] initWithDomain:NSPOSIXErrorDomain code:errno userInfo:nil], nil);
+    if (callback) callback([[NSError alloc] initWithDomain:NSPOSIXErrorDomain code:error userInfo:nil], nil);
     return;
   }