Add IsTeleTileNumberUsed function

To check whether the number of a tele tile is used or not.

src/game/editor/layer_tiles.cpp

@@ -1335,11 +1335,7 @@ bool CLayerTele::ContainsElementWithId(int Id)
 	{
 		for(int x = 0; x < m_Width; ++x)
 		{
-			if(m_pTeleTile[y * m_Width + x].m_Type == TILE_TELECHECKIN)
+			if(IsTeleTileNumberUsed(m_pTeleTile[y * m_Width + x].m_Type) && m_pTeleTile[y * m_Width + x].m_Number == Id)
-				continue;
-			if(m_pTeleTile[y * m_Width + x].m_Type == TILE_TELECHECKINEVIL)
-				continue;
-			if(m_pTeleTile[y * m_Width + x].m_Number == Id)
 			{
 				return true;
 			}

src/game/mapitems.cpp

@@ -57,6 +57,12 @@ bool IsValidTeleTile(int Index)
 		Index == TILE_TELECHECKINEVIL);
 }
 
+bool IsTeleTileNumberUsed(int Index)
+{
+	return Index != TILE_TELECHECKIN &&
+	       Index != TILE_TELECHECKINEVIL;
+}
+
 bool IsValidSpeedupTile(int Index)
 {
 	return Index == TILE_BOOST;

src/game/mapitems.h

@@ -489,6 +489,7 @@ public:
 bool IsValidGameTile(int Index);
 bool IsValidFrontTile(int Index);
 bool IsValidTeleTile(int Index);
+bool IsTeleTileNumberUsed(int Index); // Assumes that Index is a valid tele tile index
 bool IsValidSpeedupTile(int Index);
 bool IsValidSwitchTile(int Index);
 bool IsValidTuneTile(int Index);