Added User Manual and fixes

Added help button on the title screen with animation. Added User Manual to appear after clicking the button, and vice versa. Added tons of catches to handle unwanted errors.

Assets/Scripts/Player/PlayerManager.cs

@@ -32,11 +32,23 @@ public class PlayerManager : MonoBehaviour
             Destroy(playerInput.gameObject);
             return;
         }
-        Debug.Log("Player joined");
+        print("Player joined");
         DontDestroyOnLoad(playerInput.gameObject);
+        if (PlayerCardCreator.Instance == null)
+        {
+            return;
+        }
         PlayerJoinCard card = PlayerCardCreator.Instance.CreateCard();
+        if (card == null)
+        {
+            return;
+        }
         card.playerNumber = GameManager.players.Count + 1;
         cards.Add(card);
+        if (GameManager.players == null)
+        {
+            GameManager.players = new List<GameObject>();
+        }
         GameManager.players.Add(playerInput.gameObject);
         Colorize(GameManager.players.Count - 1);
     }
@@ -46,7 +58,7 @@ public class PlayerManager : MonoBehaviour
     {
         Destroy(playerInput.gameObject);
         GameManager.players.Remove(playerInput.gameObject);
-        Debug.Log("Player left");
+        print("Player left");
     }
 
     private void Init()