Fix water generation, try to improve decoration level a bit

lib/mapping/CMapOperation.cpp

@@ -292,7 +292,7 @@ void CDrawTerrainOperation::updateTerrainViews()
 
 		if(pattern.decoration)
 		{
-			if (gen->nextInt(100) > decorationsPercentage)
+			if (pattern.mapping.size() < 2 || gen->nextInt(100) > decorationsPercentage)
 				mapping = pattern.mapping[0];
 			else
 				mapping = pattern.mapping[1];

lib/rmg/RmgMap.cpp

@@ -47,7 +47,7 @@ RmgMap::RmgMap(const CMapGenOptions& mapGenOptions) :
 
 int RmgMap::getDecorationsPercentage() const
 {
-	return 10; // arbitrary value to generate more readable map
+	return 15; // arbitrary value to generate more readable map
 }
 
 void RmgMap::foreach_neighbour(const int3 & pos, const std::function<void(int3 & pos)> & foo) const