No blue outlines when selecting media in the preview window
So, I've had this issue for a little while now. The blue outlines which normally go around the borders of different media (pictures, video files, text etc) in the preview window when they're selected, have disappeared! The outlines have squares on the edges and in the exact middle of the imported media to make it easier to relocate and move them. This issue doesn't only make moving things around in the preview window harder, but also a lot less accurate. They disappeared after I miss-clicked a key when I was performing a 'CTRL+(X)' shortcut, probably the CTRL+D shortcut. and now I can't get them back. No one seems to have discussed this issue publicly before, at least not with the terms I've searched the forums and the web with. Is there a simple way to make the blue outlines come back?
As you can see in this picture, there are no typical "blue outlines" for me when selecting media in the preview window above the timeline;

Here is a picture of the outlines I'm talking about, if it's still unclear. The picture is from an old version of Adobe Premiere Pro, as I can not produce the pictures myself. I am using the latest version of Adobe Premiere Pro CC 2017.
Thanks in advance.
~Henriko
