take into account the fact that a command may return null after execu…

…ting the command

modules/feed-comm/feed-comm-war/src/main/java/org/hawkular/feedcomm/ws/command/Command.java

@@ -28,7 +28,7 @@ public interface Command<REQ extends BasicMessage, RESP extends BasicMessage> {
      *
      * @param request the request that describes what needs to be executed
      * @param context some context data that can be useful for the command to be able to execute the request
-     * @return the results of the command that need to be sent back to the feed.
+     * @return the results of the command that need to be sent back to the feed - may be null
      * @throws Exception if failed to execute the operation
      */
     RESP execute(REQ request, CommandContext context) throws Exception;

modules/feed-comm/feed-comm-war/src/main/java/org/hawkular/feedcomm/ws/server/FeedCommWebSocket.java

@@ -119,7 +119,7 @@ public String feedMessage(String nameAndJsonStr, Session session, @PathParam("fe
 
         }
 
-        String responseText = ApiDeserializer.toHawkularFormat(response);
+        String responseText = (response == null) ? null : ApiDeserializer.toHawkularFormat(response);
         return responseText;
     }
 

modules/feed-comm/feed-comm-war/src/main/java/org/hawkular/feedcomm/ws/server/UIClientCommWebSocket.java

@@ -122,7 +122,7 @@ public String uiClientMessage(String nameAndJsonStr, Session session) {
 
         }
 
-        String responseText = ApiDeserializer.toHawkularFormat(response);
+        String responseText = (response == null) ? null : ApiDeserializer.toHawkularFormat(response);
         return responseText;
     }