MMEX 1.8.1 cannot read an SUID.

If users want to revert from 1.9.0 to 1.8.1 (e.g., due to bugs in 1.9.0), they may have two problems:

• A database modified by 1.9.0 may not open in 1.8.1, or it may crash the application.
• User settings (SETTING_V1, USAGE_V1) modified by 1.9.0 may not open in 1.8.1, or may crash the application.

To overcome the first problem, users may need to cleanup all entries with SUID using 1.9.0, and then open the database file with 1.8.1. Or they can discard the database file completely and switch to a previous backup. Both solutions are inconvenient and may cause data loss.

The second problem is more difficult to overcome, because there is no backup file for user settings (at least on macOS). Users may try to remove the settings file completely and re-create it, losing all previous settings. Also some instructions are needed in order to find this file in each platform.

I experience application crashes when I temporarily switch to 1.9.0 for testing.

@guanlisheng, @whalley, @n-stein as FYI