Blank lines in formatted text lost on open

[MarcSabatella]

Issue type

Other type of issue

Bug description

In a text element containing blank lines between paragraphs/stanzas, the blank lines disappear on save/reload if the text has formatting applied to it.

Steps to reproduce

1. New score
2. Add text frame
3. Add text consisting of three lines: "aaa", a blank line, and "bbb"
4. While still in edit mode, press Ctrl+A to select the full text
5. Use Properties to set a point size of 12 pt (or something other than the default)
6. Save
7. Reopen

Result: the blank line has disappeared.

Also note, at step 5, the display of font size in the Properties panel displays "-" as if the select text is currently at different sizes. This isn't actually the case, and it's possible this erroneous report in Properties is somehow related.

Screenshots/Screen recordings

No response

MuseScore Version

OS: Debian GNU/Linux 11 (bullseye), Arch.: x86_64, MuseScore version (64-bit): 4.2.0-232380304, revision: github-musescore-musescore-0cf3725

Regression

Yes, this used to work in MuseScore 3.x and now is broken

Operating system

Debian 11, Windows

Additional context

This also fails if applying the formatting to the paragraphs/stanzas individually. But it works as expected if instead of selecting the text and applying the formatting that way, you apply the formatting to the element as a whole (eg, while not in edit mode).

This was originally reported by a user (my brother!) loading a MuseScore 3 score that had been formatted this way into MuseScore 4. I verified that the blank lines are still present when loading into MuseScore 3, but not when loaded into MuseScore 4. And verified I could reproduce it from scratch both in 4.1.1 and in current master.

Here is the original MuseScore 3 file:
American Taxation zip.zip

[rgreen5]

Perhaps some connection with #18553?