"Strict" consensus algorithm draws an empty space instead of gap if a threshold is too low

Scenario to reproduce:

1. Open "data/samples/CLUSTALW/COI.aln".
2. Set "Strict" consensus algorithm.
3. Set threshold to 1%.
4. Remove the last sequence from the MSA.
   Expected state: consensus characters in the columns, that consist of gaps, are also gaps.
   Current sate: there is empty space instead of characters in these columns.