disable traceback lines with non-existing files

src/logic/scripting/lua/libs/libfile.cpp

@@ -19,7 +19,7 @@ static fs::path resolve_path(const std::string& path) {
 
 static fs::path resolve_path_soft(const std::string& path) {
     if (path.find(':') == std::string::npos) {
-        return path;
+        return fs::u8path("");
     }
     return engine->getPaths()->resolve(path, false);
 }