Describe the bug
When running the application for the first time, I was able to run a search but it produces an error. At a guess the error is UI related; the search appears to have executed successfully.

To Reproduce
Steps to reproduce the behavior:

1. Download source, make, make run.
2. Add two large directories located on an external hard drive (probably with mostly identical content.)
3. Start a search for duplicate images based on EXIF metadata.
4. Notice search starting and progressing to at least 16%.
5. Leave PC unattended and return later to find the below error message displayed.
6. Upon closing the error window, find that the results tab is populated with a large number of duplicates, indicating the search was successful despite the error.

Expected behavior
Did not expect an error.

Screenshots
N/A

Desktop (please complete the following information):

• OS: Fedora 32
• Version 4.0.4

Additional context

Application Name: dupeGuru
Version: 4.0.4

Traceback (most recent call last):
File "/home/anlag/gitrepos/dupeguru/hscommon/gui/progress_window.py", line 109, in pulse
self._finish_func(self.jobid)
File "/home/anlag/gitrepos/dupeguru/core/app.py", line 316, in _job_completed
self.view.show_results_window()
File "/home/anlag/gitrepos/dupeguru/qt/app.py", line 362, in show_results_window
self.showResultsWindow()
File "/home/anlag/gitrepos/dupeguru/qt/app.py", line 226, in showResultsWindow
self.main_window.showTab(self.resultWindow)
File "/home/anlag/gitrepos/dupeguru/qt/tabbed_window.py", line 176, in showTab
self.setTabVisible(index, True)
File "/home/anlag/gitrepos/dupeguru/qt/tabbed_window.py", line 186, in setTabVisible
return self.tabWidget.setTabVisible(index, value)
AttributeError: 'QTabWidget' object has no attribute 'setTabVisible'