help me with this last exeption :)

hi i have this last exeption, anyone knows what it is?

<?xml version="1.0"?>
<root>
    <report>
        <version>2</version>
        <sessionid>709764a935cd2f4c5c287891</sessionid>
        <type>desync</type>
        <sku>ea.maxis.sims4.15.mac</sku>
        <createtime>2018-12-30 14:27:13</createtime>
        <buildsignature>Local.Unknown.Unknown.1.48.94.1220-1.200.000.377.Release</buildsignature>
        <categoryid>weakref.py:429</categoryid>
        <desyncid>709764a935cd2f4c5c287891</desyncid>
        <systemconfig/>
        <screenshot/>
        <desyncdata>Exception in Sim Timeline: Exception resuming Element (TypeError: cannot create weak reference to 'NoneType' object)&#xD;
        Traceback (most recent call last):&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\scheduling.py", line 217, in simulate&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\elements.py", line 385, in _resume&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\interactions\si_state.py", line 912, in process_gen&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\interactions\si_state.py", line 313, in remove_gen&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\interactions\si_state.py", line 1111, in _remove_gen&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\interactions\base\super_interaction.py", line 4656, in on_removed_from_si_state&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\interactions\social\social_super_interaction.py", line 1506, in _exited_pipeline&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\interactions\base\interaction.py", line 6983, in on_removed_from_queue&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\interactions\base\super_interaction.py", line 4488, in cancel&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\interactions\base\super_interaction.py", line 4255, in _cancel_eventually&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\interactions\social\social_super_interaction.py", line 1516, in _cancel&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\interactions\social\social_super_interaction.py", line 1569, in _detach_from_group&#xD;
          File "T:\InGame\Gameplay\Scripts\Server\socials\group.py", line 812, in detach&#xD;
          File "T:\InGame\Gameplay\Scripts\Lib\weakref.py", line 429, in get&#xD;
        TypeError: cannot create weak reference to 'NoneType' object&#xD;
        rtim=0</desyncdata>
    </report>
</root>