Actually, lava will only have 3 obstacle sets without mods

config/biomes.json

@@ -637,7 +637,7 @@
 		},
 		"templates" : ["AVLc10l0", "AVLc11l0", "AVLc12l0", "AVLc13l0", "AVLc14l0", "AVLct1l0", "AVLct2l0", "AVLct3l0", "AVLct4l0", "AVLct5l0", "AVLct6l0", "AVLct7l0", "AVLct8l0", "AVLct9l0", "AVLctrl0"]
 	},
-	"templateSet176":{
+	"lavaDeadTree":{
 		"biome":{
 			"terrain" : "lava",
 			"objectType" : "tree"

lib/mapping/ObstacleProxy.cpp

@@ -59,7 +59,7 @@ bool ObstacleProxy::prepareBiome(const ObstacleSetFilter & filter, CRandomGenera
 	std::vector<std::shared_ptr<ObstacleSet>> obstacleSets;
 
 	size_t selectedSets = 0;
-	const size_t MINIMUM_SETS = 4; // Original Lava has only 4 types of sets
+	const size_t MINIMUM_SETS = 3; // Original Lava has only 4 types of sets
 	const size_t MAXIMUM_SETS = 9;
 	const size_t MIN_SMALL_SETS = 3;
 	const size_t MAX_SMALL_SETS = 5;