GUACAMOLE-197: Check for empty byte array in more sane manner.

extensions/guacamole-auth-radius/src/main/java/org/apache/guacamole/auth/radius/RadiusConnectionService.java

@@ -290,7 +290,7 @@ public class RadiusConnectionService {
             return null;
         }
 
-        if (state == null || state.length < 1) {
+        if (state == null || state.length == 0) {
             logger.error("Challenge/response to RADIUS requires a prior state.");
             return null;
         }