Assertion Failed - abnormal program termination

See the <invalid hyperlink removed by admin> image for details.
It happens whenever I cancel the "background upload" task.
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I guess there's no reply... and no solution for this one then...
Do you want me to provide more details on this error ?

Sorry. This is known error. Unfortunatelly I have no idea what causes it yet, so I even do not know what to ask for.