allowFilterExpressions+filterOnKeypress break grid filtering

[Crack]

Entering "#" or "!#" into filter editor with both allowFilterExpressions and filterOnKeypress enabled causes grid to be filtered and entered value to disappear from filter form, making it impossible to remove this filter.

To reproduce:
1. Go to https://www.smartclient.com/smartcli...?id=liveFilter
2. Add "allowFilterExpressions: true" to grid
3. In filter for Country enter "#" or "!#"
4. Entered filter is applied and disappears from form, making it impossible to undo it.

Tested SmartClient versions:
* v11.1p_2018-04-24/AllModules Development Only
* v12.0p_2018-04-24/AllModules Development Only

[Isomorphic]

Your problem here is that "#" and "!#" ("isNull" and "notNull" operators) are not available by default - you should instead use "$" and "!$", which relate to "blank" and "notBlank" and are functionally equivalent to the null variants.

If you want to add the null operators, or any other non-default ones, see the docs for validOperators.

[Crack]

Then shouldn't filters just leave these values alone? Currently entering "#" permanently breaks filtering and requires page reload to fix.

[Isomorphic]

Yes, we'll disable this feature - of storing and applying uneditable criteria in the background - during user-edits, since it makes no sense there.

You should see the fix in tomorrow's builds.

[Isomorphic]

We've made some changes here - please retest with a build dated May 2 or later.

[Crack]

Thanks. Now users using GUI can't break their application. I will also update my in-app hints to mention blanks ($) instead of Nulls (#).