Extend line does not work in compoundCurvedZ layer

[SrNetoChan]

Describe the bug

It seems that the extend line functionality (node tool) only works editing the line starting point, but doesn't when you try to extend the final node. furthermore, this only happens when the feature is saved into the gpkg file. While only on memory it works fine.

I have tried a multilineZ layer and the problem did not show up. I was only able to reproduce using a CompoundCurveZ geopackage layer.

Here's a dataset sample

https://mega.nz/#!cYlmDaTb!0OTijkGrPWYCnuYa3zUHkrEdaCk4f5wBHNgEnnB5tng

How to Reproduce

I hope the screenshot is self-explanatory.

QGIS and OS versions

QGIS version	3.9.0-Master	QGIS code revision	QGIS code revision
Compiled against Qt	5.9.5	Running against Qt	5.9.5
Compiled against GDAL/OGR	2.2.3	Running against GDAL/OGR	2.2.3
Compiled against GEOS	3.6.2-CAPI-1.10.2	Running against GEOS	3.6.2-CAPI-1.10.2 4d2925d6
Compiled against SQLite	3.22.0	Running against SQLite	3.22.0
PostgreSQL Client Version	11.5 (Ubuntu 11.5-1.pgdg18.04+1)	SpatiaLite Version	4.3.0a
QWT Version	6.1.3	QScintilla2 Version	2.10.2
PROJ.4 Version	493
OS Version	Ubuntu 18.04.3 LTS
Active python plugins	Qgis2threejs; valuetool; DigitizingTools; mgrstools; qgistester; trackable_project_files; changeDataSource; quick_map_services; MemoryLayerSaver; firstaid; workbench; vector_tiles_reader; QuickOSM; processing; db_manager

Additional context