Bad check for query in VerboseTableResult

Problem/Motivation

Now when a sensor doesn't set the #query parameter as VerboseTableResult sets it to empty string when we check if query is empty always returns true.

Proposed resolution

We could initialize the #query to null, but as is possible that a sensor give us an empty string, I think the best option is to change the check to a !empty() instead of isset().
We have to do the same for #query_args that now works just because when we initialize it the name is incorrect.
Also we have to change that #arguments for #query_args.

Remaining tasks

User interface changes

API changes

Data model changes