A read base is selected when a single reference base is selected in MCA Editor

Scenario to reproduce:

1. Open an MCA.
2. Scroll to the place, where the first read has data.
3. Select a single base on the reference above the read.
   Expected state: only the reference base is selected, the column is highlighted.
   Current state: a read symbol is selected under the clicked reference base. Both read and column are highlighted.