Ask user before starting initial plugin scan

[apohl79]

[nodevnul]

I would go further here:

Disable Plugin-Scan by default.

Audiogridder Server crashes several times on any startup if plugins are scanned and there are no authorization methods attached to the system (e. g. iLok, USB-Stick, etc.).

Furthermore: PluginScan launches each plugin and if no authorization method can be found by the plugin then the process will stand still at this point forever. Audiogridder reports these as "slow” and lets the user skip them yet additionally throws a message about those plugins failed.

This has become so annoying…