Fixed message commands where a null optionnal argument was being parsed when it shouldn't be

src/main/java/me/bobert/netneutrality/context/MessageCommandContext.java

@@ -268,7 +268,10 @@ public class MessageCommandContext extends CommandContext {
                 invalidateContext(data, "the argument provided was not a number.");
             }
 
+            if (value != null) {
                 options.add(new MessageCommandOption(data, value));
+            }
+
             index++;
         }