fdo#77735: Write test for this.  This test will freeze with the bug present.

Change-Id: I7b7e67fe2ee59b57ce74f8303d30bebc84f6b0d0
fdo#77735: Don't proceed when all cells in the range are empty.

That means there is nothing to delete, and proceeding would cause Calc
to freeze.

Change-Id: I2a8fb5736870ba459082873c8f864283d8b9c664