FYI: Locking yourself out is possible.

[Innomen]

Assume latest versions. This is a courtesy.

If you have no free spaces but lock widgets there's almost no way to unlock them except by exporting/importing your settings. This forces the creation of an empty page, and from there you can long touch an empty space to access the menu for unlocking.

[mborkunov]

You can still open OpenLauncher settings (it should be available in the applications list) and increase the desktop size. After that you will get an empty space in your desktop grid.

[blhiggins]

I just fell into this trap myself. Without knowing that you can unlock the screen if there's a blank space on it, it's a bit disconcerting to lock the screen and then for there to be no discoverable way to unlock it again.

Might I propose this issue be turned into a suggestion: Can there be a "Lock widgets" checkbox added to the Desktop section of Settings? A user in this situation could then discover that checkbox and uncheck it. I think that would be reasonable - it's where I first thought to go looking for a solution, at least.