Fix merge mistake

Author: electricbrass

common/m_fileio_posix.cpp

@@ -139,7 +139,7 @@ std::string M_GetUserDir()
 {
 	fs::path path = M_GetHomeDir();
 	path /= ".odamex";
-	return path;
+	return path.string();
 }
 
 std::string M_GetWriteDir()