title: Qt/C++: Icons not showing up when program is run
body: <p>I've added a <code>QAction</code> to my <code>QToolBar</code> in my MainWindow in Qt Designer (using the Qt Creator IDE) and given that Action an icon (done by "Choose File" and selecting my .png located in the same directory as my project and source code). The icon shows up fine in the toolbar in Qt Designer, but does not show when the project is running. I've had similar trouble when choosing the title bar icon on windows. I've never used graphics in Qt before, is there something special I need to do?  </p>
  
  <p>Screenshot:<br>
  <img src="https://i.imgur.com/e4vAz.png" /></p>