Disable the shortcut controls when an action has not been selected

Add this to your merge proposal:
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lp:~raoul-snyman/openlp/custom-shortcuts-2.4 (revision 2681)
[SUCCESS] https://ci.openlp.io/job/Branch-01-Pull/1952/
[SUCCESS] https://ci.openlp.io/job/Branch-02-Functional-Tests/1863/
[SUCCESS] https://ci.openlp.io/job/Branch-03-Interface-Tests/1804/
[SUCCESS] https://ci.openlp.io/job/Branch-04a-Windows_Functional_Tests/1530/
[SUCCESS] https://ci.openlp.io/job...