How can I delete empty lines in OpenOffice Calc?
Select all (CTRL+A);
Sort alphabetically+crescent (select that button in toolbar or Data > Classify > Choose by the first column and crescent);
So you will have all empty rows at the end and you will have to remove only if there is some formatting.
That technique would not be much efficient if you have sparse data (a lot of empty cells between data) in "table" without a "custom header" (if you have not put the first line with the name of columns).
PS: Sometimes when I sort data on table, it sorts also the header, so it is moved from the top of worksheet to another position. To avoid that, freeze header row/rows before sorting.