Merge lines in direction error

[AlisterH]

Merge lines in direction produces this rather incomprehensible error if there is a line that starts and ends at the same point:

Calculating feature informations...
Merging lines...
Saving output...
Traceback (most recent call last):
File "C:\Users/alister/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\lftools\processing_provider\Vect_DirectionalMerge.py", line 334, in processAlgorithm
fet.setGeometry(QgsGeometry.fromPolylineXY(item[0]))
TypeError: index 0 has type 'float' but 'QgsPointXY' is expected

Execution failed after 0.01 seconds