Can't Close Masteries [CLIENT]

When i drag the client to the side to look at google, then click masteries, the x button is unclickable, and i can't move the client back into the center of my screen to click the x. I would think you could add something where you can just press escape(on the keyboard). When this happens to me i have no choice but to quit the client and reopen it.[slayer-jinx-unamused] How to get this:

1. Open the client(duh)
2. Drag client to the side of the screen
3. Open masteries