Zero-length notes copied from the B&B editor cause incorrect behavior in the song editor

[musikBear]

Bug Summary

Notes copied from the B&B editor do not get registered as notes in the song editor. The block with the notes remains empty and grey.
In the picture on the left, you can see the grey block. Its length is extended, but there is no visible content. On the right, you can see the notes actually in the block.

(The block will appear to have no content, but content is played anyway)

Steps to reproduce

Recreate:

• Add some content to the default kicker patch in the B&B editor
• Open the pattern content in the piano roll
• Select all and copy
• Open a new clip on an instrument in the song editor and paste the notes

Expected behavior

The clip turns green and extends in length.

Actual behavior

The clip does not turn green, but the length is still extended.

LMMS version used

LMMS 1.2.1 on Windows 10

SecondFlight: migrated info to issue description and reworded some things