Error if click in consensus area of an empty file

Scenario:

1. Open an empty alignment, e.g. "_common_data/fasta/empty.fa".
2. Click in the consensus area.
   Expected state: Nothing happens.
   Actual state: There is a safe point:

   [ERROR][16:37] Trying to recover from error: No rows at src\datatype\msa\MultipleAlignment.cpp:215