An empty QTextDocument already contains a block; so when the formatting
is fully determined, if the document is still empty, then instead of
inserting a new block, we can set formatting on the cursor, which
affects the pre-existing block, before inserting text. This avoids
leaving a blank line (the default block) above the inserted content.
Fixes: QTBUG-81060
Change-Id: I14e45e300a602493aa59680417d74d4c2b25862d
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
76fbe75abe