bezier tool - smooth node bug (after creation, some are turned to cusp nodes)

Migrated from: https://bugs.launchpad.net/inkscape/+bug/1666932

Steps to reproduce:

• Open Inkscape
• Take a bezier tool
• Create the first point with curve handle (click+ drag )
• Create the second point with smooth mode
• Creat 3thid point without smooth node(corner point)
• Take node tool and check geometry

What happened?

• The second node is corner point with broken (unlinked) handles

• This bug happens in multiple other situations (with corner node without any handles, a first node of the path, or last node of the path)

What should have happened?

• Second node should be a smooth node

• Smooth nodes should stay smooth

Inkscape Version and Operating System:

• Inkscape Version: 1.0alpha (7076368, 2019-01-18)
• Operating System: WIN 10
• Operating System version: 1908

Example: https://streamable.com/rkeko