dragons: apply crashfix by jackdavidson

dragons/eggs.lua

@@ -41,7 +41,11 @@ local function egg_transform(pos, node, clicker, item, _)
 				break
 			end
 		end
-		
+
+        if dragon_type == nil then
+            return
+        end
+
 		minetest.chat_send_player(clicker:get_player_name()," ... something seems to be happening .... come back later?")
 		
 		minetest.after(dmobs.eggtimer,