Fix saved inputs on Edit Exercise page

[sktran]

While I was updating the list of exercises (for formatting and description), I noticed that the "saved inputs" for Most Important Joint are not displayed correctly.

For example, when I created the exercise for Hip Abduction, Left Leg, I definitely selected "Left Ankle" as its most important joint. However, when I go to edit this exercise, I see that the Most Important Joint field is set to "Neck", which is the default. When I change this back to "Left Ankle" and click "Update", I do not get a successful confirmation message and am immediately directed back to the Exercises page.

When I go back into the page for Hip Abduction, Left Leg, the Most Important Joint is again back to "Neck". It should display "Left Ankle". See screenshot below.

Note: I was logged in as the root user.