When querying a column which has a null value (empty cell) somewhere in it, the result set is missing all the rows under the null value in the xlsx file. When querying more columns, the result set is missing some values only if there is a row, where both columns contains null value.

Affected version:
DV 6.1.0 ER4

Steps to reproduce:
1. Create excel spreadsheet with some cells with null values. Ideally a few rows should follow the null-valued cells.
2. Create and deploy vdb
3. Query the vdb selecting the columns with some null values
4. When all the columns in select clause are null, the following rows are not returned.