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

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

00:16:10

passed #1690
golang mongo goqt
Integration tests

00:02:43

passed #1692
strong mongo golang
Unit tests

00:03:35

failed #1689
golang mongo strong
Unit tests

00:01:38