fixed issue with ssh_connector when data has been consumed by a channel callback

Signed-off-by: Jeremy Cross <jcross@beyondtrust.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

src/connector.c

@@ -446,6 +446,9 @@ static int ssh_connector_channel_data_cb(ssh_session session,
     } else if (!is_stderr && !(connector->in_flags & SSH_CONNECTOR_STDOUT)) {
         /* ignore stdout */
         return 0;
+    } else if (len == 0) {
+        /* ignore empty data */
+        return 0;
     }
 
     if (connector->out_wontblock) {