A GUI deadlock in Sitecon and Weight matrix search dialogs

Scenario to reproduce #1:

1. Open "data/samples/FASTA/human_T1.fa".
2. Open a "SITECON Search" dialog, fill it and start the search.
   Expected state: the dialog is opened, there are search results.
3. Click the "Save as annotations" button and then click the "Search" button again before all annotations are drawn.
4. Try to close the dialog.
   Expected state: the dialog is closed, the search task is canceled.
   Current state: GUI waits until all annotations are drawn, then react on the button click.

Scenario to reproduce #2:

1. Open "data/samples/FASTA/human_T1.fa".
2. Run "Auto-annotations update" task, e.g. find tandems with default parameters.
3. Open a "SITECON Search" dialog before "auto-annotations update" task finish, fill it and start the search.
   Current state: a deadlock occurs: "auto-annotations update" task wait until the dialog close, dialog can't be closed until the search task finish, the search task waits until the "auto-annotation update" task finish.

The same scenarios are repeatable with the "Weight Matrix Search" dialog.
Check other dialogs.