Fix bug #1547964 by ignoring the exception (it's harmless)


Add this to your merge proposal:
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lp:~raoul-snyman/openlp/disconnect-slots-2.4 (revision 2652)
[SUCCESS] https://ci.openlp.io/job/Branch-01-Pull/1741/
[SUCCESS] https://ci.openlp.io/job/Branch-02-Functional-Tests/1652/
[SUCCESS] https://ci.openlp.io/job/Branch-03-Interface-Tests/1590/
[SUCCESS] https://ci.openlp.io/job/Branch-04a-Windows_Functional_Tests/1346/
[SUCCESS] https://ci.openlp.io/job/Branch...