Fix an unlikely modding hang.

Author: sprunk

LuaUI/Widgets/unit_start_state.lua

@@ -1147,8 +1147,16 @@ local function AddFactoryOfUnits(defName, plateDefName)
 		addUnit(plateDefName, name)
 	end
 	for i = 1, #ud.buildOptions do
-		addUnit(UnitDefs[ud.buildOptions[i]].name, name)
-		unitsToFactory[UnitDefs[ud.buildOptions[i]].name] = defName
+		local buildeeDef = UnitDefs[ud.buildOptions[i]]
+		local buildeeDefName = buildeeDef.name
+		addUnit(buildeeDefName, name)
+
+		-- sufficiently insane mods can have factories build each other,
+		-- leading to infinite recursion with "inherit from fac" states
+		if not buildeeDef.isFactory then
+
+			unitsToFactory[buildeeDefName] = defName
+		end
 	end
 end