add some extra null checks in biofluid

changelog.txt

@@ -7,6 +7,7 @@ Date: ???
     - Nerfed scrondrix path 1. No longer grants bonus cubs
     - Buffed scrondrix path 2. Multiplies meat by 3x instead of 5x. No more -20% speed downgrade
     - Nerfed composter path 1. Dried biomass amount reduced 12 -> 4
+    - Fixed improper migrations to new biofluid system causing crashes (https://github.com/pyanodon/pybugreports/issues/367)
 ---------------------------------------------------------------------------------------------------
 Version: 2.1.13
 Date: 2024-1-8

migrations/biofluid.lua

@@ -0,0 +1,5 @@
+--for _, surface in pairs(game.surfaces) do
+    --for _, pipe in pairs(surface.find_entities_filtered{name = {'vessel', 'bioport'}}) do
+        --pipe.destroy()
+    --end
+--end

scripts/biofluid/biofluid.lua

@@ -364,17 +364,19 @@ local function find_new_home(biorobot_data, network_data)
 	local home
 	local min_robot_count = 999
 	for unit_number, bioport in pairs(network_data.bioports) do
-		local bioport_data = global.biofluid_bioports[bioport.unit_number]
-		if unit_number ~= old_home and bioport.valid and bioport_data then
-			local robot_count = bioport.get_inventory(INPUT_INVENTORY).get_item_count(biorobot_data.entity.name)
-			if robot_count < 6 then
-				home = bioport
-				biorobot_data.bioport = unit_number
-				break
-			elseif robot_count < min_robot_count then
-				min_robot_count = robot_count
-				home = bioport
-				biorobot_data.bioport = unit_number
+		if bioport.valid then
+			local bioport_data = global.biofluid_bioports[bioport.unit_number]
+			if unit_number ~= old_home and bioport.valid and bioport_data then
+				local robot_count = bioport.get_inventory(INPUT_INVENTORY).get_item_count(biorobot_data.entity.name)
+				if robot_count < 6 then
+					home = bioport
+					biorobot_data.bioport = unit_number
+					break
+				elseif robot_count < min_robot_count then
+					min_robot_count = robot_count
+					home = bioport
+					biorobot_data.bioport = unit_number
+				end
 			end
 		end
 	end

scripts/biofluid/network-builder.lua

@@ -194,6 +194,7 @@ function Biofluid.built_pipe(entity, update_graphics)
 end
 
 function Biofluid.is_looking_at_us(entity, connection, network_positions)
+	if not entity.valid then return nil end
 	if not network_positions then
 		network_positions = Biofluid.network_positions(entity.surface_index)
 	end