Variables: Fixes maximum call stack bug for empty value

[hugohaggmark]

What this PR does / why we need it:
When using an empty value for a Text variable the logic that checked for variable changes in URL got into an endless loop. This PR tries to remedy this.

Which issue(s) this PR fixes:
Fixes #25485

Special notes for your reviewer:

[aocenas]

Not sure how related this is but seem like the variable is not preserved in the url. If I save the dashboard and then open it in separate tab it shows the variable filled in but it isn't in the url and it seems to start working only after I click into the input and out.

[hugohaggmark]

Not sure how related this is but seem like the variable is not preserved in the url. If I save the dashboard and then open it in separate tab it shows the variable filled in but it isn't in the url and it seems to start working only after I click into the input and out.

good catch, will look into this!

[hugohaggmark]

Not sure how related this is but seem like the variable is not preserved in the url. If I save the dashboard and then open it in separate tab it shows the variable filled in but it isn't in the url and it seems to start working only after I click into the input and out.

If I understand your comment right @aocenas this is the intended behavior for all variables.

[hugohaggmark]

Is there some additional work that is needed before approval here @aocenas @tskarhed

[tskarhed]

Looks good! Error is no longer there!

[aocenas]

@hugohaggmark
So there was still some issues based on the conversations in slack mainly:

But you should not come to the state when you see query: some text while the actual value is something else.

This still seems like a bug to me.

[aocenas]

But I am ok if that is solved separately.

[hugohaggmark]

Would be great if you could file that as a separate issue @aocenas 🙏