utils: readCompleteFile(): Throw exception if file can't be opened

utils.cpp

@@ -138,6 +138,10 @@ std::string utils::readCompleteFile(std::string_view filepath)
 {
 
 	std::fstream stream(std::string{filepath});
+	if(!stream.is_open())
+	{
+		throw std::runtime_error("stream is not open");
+	}
 	std::stringstream ss;
 	ss << stream.rdbuf();
 	std::string content = ss.str();