Bug that allows to create empty function defs or equations

[PetitFrapo]

Describe the bug
It is possible to create an empty function or equation. It is not super bad, but it still is a bug.

To Reproduce
Steps to reproduce the behavior:

1. Go to the Functions or Equations app.
2. Click on Add function/equation.
3. Leave blank, and simply press SHIFT+1, 3, or any input that won't type an omega, mu, or that isn't the current app.
4. Upon coming back to the original app, there will be an empty function/equation.

Expected behavior
I did this on complete accident, and when then after trying to reproduce what I did, I managed to remember my inputs. The bug doesn't lead to any breakage. With an empty function, trying to calculate for instance f(4) in the Calculation app will simply yield f(4), same for anything that involves said function. With an empty equation, if you add two more equations that would make for a linear system with 2 variables, Upsilon will show that the system is non-linear nonetheless.

Screenshots

Device (please complete the following information):

• NumWorks N0110 with Upsilon.
• Upsilon Version: 1.0.1-dev
• Upsilon commit: 9ac62c0

[PetitFrapo]

Well, turns out it's even easier than I thought.
To do it you actually only need to get on the Add function/equation entry box (where you type the expression), click Backspace as if you were deleting nothing and then press Back (the rightmost button of the topmost line) and it works.