Don't allow the last behavior to be removed from a pCampbot bot

If you want to stop existing behavious, add the None behaviour.

OpenSim/Tools/pCampBot/Bot.cs

@@ -208,6 +208,9 @@ namespace pCampBot
 
         public bool RemoveBehaviour(string abbreviatedName)
         {
+            if (Behaviours.Count <= 0)
+                return false;
+
             Dictionary<string, IBehaviour> updatedBehaviours = new Dictionary<string, IBehaviour>(Behaviours);
             IBehaviour behaviour;
 

OpenSim/Tools/pCampBot/BotManager.cs

@@ -604,7 +604,7 @@ namespace pCampBot
                 }
 
                 MainConsole.Instance.OutputFormat(
-                    "Removed behaviours {0} to bot {1}", 
+                    "Removed behaviours {0} from bot {1}", 
                     string.Join(", ", behavioursRemoved.ConvertAll<string>(b => b.Name).ToArray()), bot.Name);
             }
         }