Template composer contents become blank when going fullscreen and back quickly

To reproduce:

• Go to the channel manager, and choose a channel
• Click "Edit template"
• Click "Fullscreen" and then "Exit fullscreen" before the button can become disabled

Expected: The button should be disabled immediately, or fullscreen should be exited normally.
Actual: Fullscreen is exited, but the template composer remains empty (white).

Happens only on Firefox or Chrome. IE doesn't seem to have the issue.