PluggableAuth crash with unknown user

I installed the PluggableAuth V1.0.0 just to see what would happen.

If I login with a valid username and password everything works fine, i get authenticated againist PDS's database user table.

However if I attempt to login in with a bad username or password I get the following exception:

"Uncaught Exception while running
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The error

The message of the error is as follow:

Unable to implement auth plugin

The error occurred in file C:\Dev\xampp\htdocs\phpdev\plugins\PluggableAuth\includes\AUTH_login.class.php at line 48"

When I uninstall the plugin I no longer get the exception when I login with a bad username or password. I only get the standard invalid username or password error message.

Is this normal behavior for this plugin?