Safely get active stage, handles case where no stage present.

Ignore blank lines and Lua style comments in conversation string.
SetParams checks input params in order of priority, handles some cases of missing params (not all yet)

Assets/Fungus/Thirdparty/FungusLua/Scripts/ConversationManager.cs

@@ -8,7 +8,6 @@ namespace Fungus
 {
 	public class ConversationManager
 	{
-		protected Stage stage;
 		protected Character[] characters;
 
 		protected Character currentCharacter;
@@ -23,12 +22,21 @@ namespace Fungus
 
 		public ConversationManager ()
 		{
-			stage = Stage.activeStages[0];
-			
 			// cache characters for faster lookup
 			characters = GameObject.FindObjectsOfType<Fungus.Character>();
 		}
 
+        protected Stage GetActiveStage()
+        {
+            if (Stage.activeStages == null ||
+                Stage.activeStages.Count == 0)
+            {
+                return null;
+            }
+
+            return Stage.activeStages[0];
+        }
+
 		/// <summary>
 		/// Parse and execute a conversation string
 		/// </summary>
@@ -91,6 +99,8 @@ namespace Fungus
 					sayDialog.SetCharacter(currentCharacter);
 				}
 
+                Stage stage = GetActiveStage();
+
 				if (stage != null && currentCharacter != null && (currentPortrait != previousPortrait || currentPosition != previousPosition))
 				{
 					PortraitOptions portraitOptions = new PortraitOptions(true);
@@ -102,6 +112,12 @@ namespace Fungus
 					stage.Show(portraitOptions);
 				}
 				
+                // Ignore Lua style comments and blank lines
+                if (text.StartsWith("--") || text.Trim() == "")
+                {
+                    continue;
+                }
+
 				exitSayWait = false;
 				sayDialog.Say(text, true, true, true, false, null, () => {
 					exitSayWait = true;
@@ -123,29 +139,81 @@ namespace Fungus
 		/// <param name="sayParams">The list of say parameters</param>
 		private void SetParams(string[] sayParams)
 		{
+            Character character = null;
 			Sprite portrait = null;
 			RectTransform position = null;
 
-			//find the character first, since we need to get its portrait
-			for (int i = 0; i < sayParams.Length; i++)
+			// try to find the character first, since we need to get its portrait
+            int characterIndex = -1;
+			for (int i = 0; character == null && i < sayParams.Length; i++)
 			{
 				for (int j = 0; j < characters.Length; j++)
 				{
 					if (characters[j].NameStartsWith(sayParams[i]))
 					{
-						currentCharacter = characters[j];
+                        characterIndex = i;
+                        character = characters[j];
 						break;
 					}
 				}
 			}
 
-			for (int i = 0; i < sayParams.Length; i++)
-			{
-				if (portrait == null) portrait = currentCharacter.GetPortrait(sayParams[i]);
-				if (position == null) position = stage.GetPosition(sayParams[i]);
-			}
-			currentPosition = position;
-			currentPortrait = portrait;
+            // Assume last used character if none is specified now
+            if (character == null)
+            {
+                character = currentCharacter;
+            }
+
+            // Next see if we can find a portrait for this character
+            int portraitIndex = -1;
+            if (character != null)
+            {
+                for (int i = 0; i < sayParams.Length; i++)
+                {
+                    if (portrait == null && 
+                        character != null &&
+                        i != characterIndex) 
+                    {
+                        Sprite s = character.GetPortrait(sayParams[i]);
+                        if (s != null)
+                        {
+                            portraitIndex = i;
+                            portrait = s;
+                            break;
+                        }
+                    }
+                }
+            }
+
+            // Next check if there's a position parameter
+            Stage stage = GetActiveStage();
+            if (stage != null)
+            {
+                for (int i = 0; i < sayParams.Length; i++)
+                {
+                    if (i != characterIndex &&
+                        i != portraitIndex)
+                    {
+                        position = stage.GetPosition(sayParams[i]);
+                        break;
+                    }
+                }
+            }
+
+            if (character != null)
+            {
+                currentCharacter = character;
+            }
+                
+            if (portrait != null)
+            {
+			    currentPortrait = portrait;
+            }
+
+            if (position != null)
+            {
+                currentPosition = position;
+            }
 		}
 	}
 }