[2.0.65] Selector combinator update interval field does not take math expressions

[Kazarme]

Reproduction steps:
1. Create a selector combinator.
2. Set the mode to "Random input".
3. Set update interval to any value other than 0
3. Attempt to input any special characters related to an equation

Expected behavior:
The value set for "Update interval" should be shown as an equation until user deselects the value box then it'll calculate the equation.

Actual behavior:
The value deletes any special characters and replaces itself with 0