Added parameter check to Process method in CommandEngine.cs.

RecrownedGTK.Tools/CommandProcessor/CommandEngine.cs

@@ -34,6 +34,9 @@ namespace RecrownedGTK.Tools.CommandProcessor
 
         public void Process(IUserInput userInput, IUserOutput userOutput, string commandAndArguments)
         {
+            if (userInput == null || userOutput == null || commandAndArguments == null) {
+                throw new ArgumentNullException("No arguments should be null.");
+            }
             string command = commandAndArguments;
             string[] arguments = null;
 
@@ -75,6 +78,11 @@ namespace RecrownedGTK.Tools.CommandProcessor
             GetCommand(command).Run(userInput, userOutput, arguments);
         }
 
+        /// <summary>
+        /// Check if the command exists using it's invokes string.
+        /// </summary>
+        /// <param name="command">A string that will invoke the command.</param>
+        /// <returns></returns>
         public bool ContainsCommand(string command)
         {
             for (int i = 0; i < commands.Count; i++)