Task member becomes invalid during the task execution

Scenario:

1. Open "Tools -> NGS data analysis -> Raw DNA-Seq data processing..." workflow and run it several (3-4) times. The idea of this step is to make Task Scheduler "very busy".
   Expected result:  the "Tasks" window now have several running task (see picture 1).
2. Now you have several "Workflow designer - Processing of raw DNA-Seq single-end reads" pages - close them all to simplify  the following process.
3. Open "Tools -> NGS data analysis -> Raw DNA-Seq data processing..." workflow again and close the appeared "Workflow designer" page very quickly. 
   Expected result:  If you do everything right and managed to do it fast you will have the same situation as at the picture 2 - the "Load Workflow scene" task is still in progress, but the "Workflow designer" window is closed. If there is no "Load Workflow scene" task repeat steps from 1 to 3 again.
4. Wait for the "Load Workflow scene" task finishing.
5. Expected result:  the "Load Workflow scene" task finished without problems.
   Actual result:  UGENE crashed.

Technical explanation: the crash appears in "WorkflowSceneIOTasks.cpp" file, line 106. The problem is, then you closed "Workflow designer" (step 3), the"WorkflowScene* scene" class member was destroyed. Usually, this task process fast enough, so you are not able to manage to close "Workflow designer" before loading task is finished, but, if Task Scheduler is overloaded, it's possible. 

This problem was found due to the Crash Report №23159