"Call Variants with SAMtools" sample executed with error "Not enough assemblies"

The issue is not reproduced in the released UGENE version 1.31.1, only on the master branch.

Scenario:

1. Open the WD.
2. Open "Call variants with SAMtools" sample workflow.
3. Select "Read Assembly (BAM/SAM)" and add
   "_common_data/bam/chrM.sorted.bam".
4. Select "Read Sequence" and add "_common_data/cmdline/call-variations/chrM.fa".
5. Run the workflow.
   Expected result: there are no errors, "variants.vcf" file is created.
   Actual result: "Not enough assemblies" error appears.

Affected tests:
GUITest_regression_scenarios_test_1735
GUITest_regression_scenarios_test_2192
GUITest_regression_scenarios_test_2569
GUITest_regression_scenarios_test_2662