QSortFilterProxyModel Q_Assert cm message.

[pkj]

I have a model(lets call it base model) on which various QSortFilterProxyModel are connected.
In the base model (hierarchial) I call beginRemoveRows and endRemoveRows(). This leads to a Q_ASSERT message from QSortFilterProxyModel as:
ASSERT: "cm" in file itemviews/qsortfilterproxymodel.cpp line 935.
Now, it seems like a bug. But it is terrible in reproduction. It only happens some times. And I don't get any documentation for this assert. Can anyone tell me what this error signifies?

[pkj]

Created bug for the same. Perhaps need to write some minimum working code to recreate it too.