FIX: Should prevent a possible buffer overflow in default config file path detection

src/base/config.c

@@ -211,7 +211,7 @@ config_default_file(char *dest, size_t len)
     } else {
         LOG_DEBUG("CONFIG", "Using XDG_CONFIG_HOME: %s", home);
         safe_strncpy(dest, home, len - 1);
-        strncat(dest, "/lektor/lektor.ini", len - 1);
+        strncat(dest, "/lektor/lektor.ini", len - 1 - strlen(home));
     }
 }