Foswiki error on every "Save" when enabling ActionTrackerPlugin

gistfile1.txt

| 2016-07-28T20:10:52+00:00 error | Attempt to reload Foswiki/Plugins/ActionTrackerPlugin/Action.pm aborted.
Compilation failed in require at /var/www/foswiki/lib/Foswiki/Plugins/ActionTrackerPlugin.pm line 483.
 at /var/www/foswiki/lib/Foswiki/Plugins/ActionTrackerPlugin.pm line 483.
        Foswiki::Plugins::ActionTrackerPlugin::lazyInit("Sandbox", "SandboxSandy") called at /var/www/foswiki/lib/Foswiki/Plugins/ActionTrackerPlugin.pm line 347
        Foswiki::Plugins::ActionTrackerPlugin::beforeSaveHandler("-- Main.MarcoPoli - 28 Jul 2016\x{a}", "SandboxSandy", "Sandbox", Foswiki::Meta=HASH(0x7fc529315998)) called at /var/www/foswiki/lib/Foswiki/Plugin.pm line 311
        Foswiki::Plugin::invoke(Foswiki::Plugin=HASH(0x563df70b7b50), "beforeSaveHandler", "-- Main.MarcoPoli - 28 Jul 2016\x{a}", "SandboxSandy", "Sandbox", Foswiki::Meta=HASH(0x7fc529315998)) called at /var/www/foswiki/lib/Foswiki/Plugins.pm line 380
        Foswiki::Plugins::dispatch(Foswiki::Plugins=HASH(0x7fc524459610), "beforeSaveHandler", "-- Main.MarcoPoli - 28 Jul 2016\x{a}", "SandboxSandy", "Sandbox", Foswiki::Meta=HASH(0x7fc529315998)) called at /var/www/foswiki/lib/Foswiki/Meta.pm line 1976
        Foswiki::Meta::save(Foswiki::Meta=HASH(0x7fc529315998)) called at /var/www/foswiki/lib/Foswiki/UI/Save.pm line 687
        Foswiki::UI::Save::__ANON__() called at /usr/share/perl5/Error.pm line 416
        eval {...} called at /usr/share/perl5/Error.pm line 408
        Error::subs::try(CODE(0x7fc5440a6418), HASH(0x7fc5441c8958)) called at /var/www/foswiki/lib/Foswiki/UI/Save.pm line 705
        Foswiki::UI::Save::save(Foswiki=HASH(0x7fc529348c80)) called at /var/www/foswiki/lib/Foswiki/UI.pm line 374
        Foswiki::UI::__ANON__() called at /usr/share/perl5/Error.pm line 416
        eval {...} called at /usr/share/perl5/Error.pm line 408
        Error::subs::try(CODE(0x7fc5440bb618), HASH(0x7fc54417a630)) called at /var/www/foswiki/lib/Foswiki/UI.pm line 500
        Foswiki::UI::_execute(Foswiki::Request=HASH(0x7fc5240b2b60), CODE(0x7fc51c085448), "save", 1) called at /var/www/foswiki/lib/Foswiki/UI.pm line 326
        Foswiki::UI::handleRequest(Foswiki::Request=HASH(0x7fc5240b2b60)) called at /var/www/foswiki/lib/Foswiki/Engine/Apache.pm line 91
        Foswiki::Engine::Apache::run(Apache2::RequestRec=SCALAR(0x7fc5286db698)) called at -e line 0
        eval {...} called |