Too big region can be set in the Find Pattern Widget

Scenario to reproduce:

1. Open "data/samples/FASTA/human_T1.fa".
2. Open "Find Pattern" options panel tab.
3. Set "Selected" region type.
4. Call context menu on the sequence view, and select "Select sequence regions...".
5. Accept the dialog with default values (a single region, from min to max).
   Expected state: the region selector widget contains "Selected" region type, region is (1..199950).
   Current state: the region selector widget contains "Selected" region type, region is (1..199951).