Fix memory leak in QuickOpenWidget

- Qt Doc: "The event is not deleted when the event has been sent.
           The normal approach is to create the event on the stack..."
- Found by clang 10 static analyzer
1 job for !163 with fix_quickopen_memleak in 61 minutes and 5 seconds (queued for 3 seconds)
detached
Status Job ID Name Coverage
  Build
failed #72702
linux kf5-qt5 qt5.12

01:01:05

 
Name Stage Failure
failed
linux kf5-qt5 qt5.12 Build The script exceeded the maximum execution time set for the job
        Start  75: test_micommandqueue
75/123 Test #75: test_micommandqueue ..................... Passed 0.75 sec
Start 76: test_lldb
kf.init.klauncher: new app ":1.41"
kf.init.klauncher: new app "org.kdevelop.kdevplatform-lock-6f6c04c4-bd79-4260-a1bd-7eb727ab23b6"
76/123 Test #76: test_lldb ............................... Passed 5.26 sec
Start 77: test_lldbformatters
kf.init.klauncher: new app ":1.42"
ERROR: Job failed: execution took longer than 1h0m0s seconds