GUAC-881: Properly handle missing parameter values.

guacamole/src/main/java/org/glyptodon/guacamole/net/basic/HTTPTunnelRequest.java

@@ -61,7 +61,12 @@ public class HTTPTunnelRequest implements TunnelRequest {
 
     @Override
     public List<String> getParameterValues(String name) {
-        return Arrays.asList(request.getParameterValues(name));
+
+        String[] values = request.getParameterValues(name);
+        if (values == null)
+            return null;
+        
+        return Arrays.asList(values);
     }
     
 }

guacamole/src/main/java/org/glyptodon/guacamole/net/basic/websocket/jetty9/WebSocketTunnelRequest.java

@@ -77,7 +77,12 @@ public class WebSocketTunnelRequest implements TunnelRequest {
 
     @Override
     public List<String> getParameterValues(String name) {
-        return Arrays.asList(handshakeParameters.get(name));
+
+        String[] values = handshakeParameters.get(name);
+        if (values == null)
+            return null;
+
+        return Arrays.asList(values);
     }
     
 }