Long space names overflow the Spaces drop-down

If a Space is created with a long name (and no spaces), when it appears in the 'Spaces' drop-down at the top of the screen, it will not wrap, and will overflow the drop-down box.

Steps to Recreate:
1. Create a new space with a name such as ConfluenceTestSpace_6.1.3_Long_Name_To_Test_Overflow
2. After creating the space, click the 'Spaces' drop-down at the top of the screen, and you will see the new space overflowing the box.

Tested on Chrome, Safari, and Firefox. All show the issue. Screenshot from Chrome is attached.