Throw an error for invalid classes

include/engine/datafacade_factory.hpp

@@ -102,7 +102,11 @@ template <template <typename A> class FacadeT, typename AlgorithmT> class DataFa
         for (const auto &name : params.avoid)
         {
             auto class_mask_iter = name_to_class.find(name);
-            if (class_mask_iter != name_to_class.end())
+            if (class_mask_iter == name_to_class.end())
+            {
+                return {};
+            }
+            else
             {
                 mask |= class_mask_iter->second;
             }

include/extractor/scripting_environment.hpp

@@ -53,6 +53,7 @@ class ScriptingEnvironment
     virtual const ProfileProperties &GetProfileProperties() = 0;
 
     virtual std::vector<std::vector<std::string>> GetAvoidableClasses() = 0;
+    virtual std::vector<std::string> GetClassNames() = 0;
     virtual std::vector<std::string> GetNameSuffixList() = 0;
     virtual std::vector<std::string> GetRestrictions() = 0;
     virtual void ProcessTurn(ExtractionTurn &turn) = 0;

include/extractor/scripting_environment_lua.hpp

@@ -60,6 +60,7 @@ class Sol2ScriptingEnvironment final : public ScriptingEnvironment
 
     std::vector<std::vector<std::string>> GetAvoidableClasses() override;
     std::vector<std::string> GetNameSuffixList() override;
+    std::vector<std::string> GetClassNames() override;
     std::vector<std::string> GetRestrictions() override;
     void ProcessTurn(ExtractionTurn &turn) override;
     void ProcessSegment(ExtractionSegment &segment) override;