The "Region" combobox switches incorrectly in the Find Pattern OP tab

1. Open file "data/samples/FASTA/human_T1.fa"
2. Press "Ctrl+F"
Expected state: Find Pattern widget has appeared
3. In the "Search in" section find the "Region" combobox. Switch it to "Custom region"
4. Set the following region: [1, 10000]
5. Set "Region" to "Whole sequence" again
Expected state: the value has changed in the combobox, region coordinates fields has disappeared, the find task has started
Current state: Nothing changed in the widget, but the find task has started and finished correctly.