[gui][c] Fix unmarshal when corrupted dfss json

Fix #10
4 jobs for fix_open_contract_crash
Status Name Job ID Coverage
  Test
passed Code lint #1691
golang lint

00:16:10

passed Integration tests #1690
golang mongo goqt

00:02:43

passed Unit tests #1692
strong mongo golang

00:03:35

failed Unit tests #1689
golang mongo strong

00:01:38