Problem/Motivation

Coming from #2010898: Use tokens for entity selection view arguments:
How to reproduce:
* Create a view with a contextual filter
* In contextual filter open the "Exceptions" fieldset and set "Exception value" to an empty string
* Run th eview with an empty argument

Expected:
* Filter is ignored and all values are shown

Experienced:
* No query is done
This is also reported in #2010898: Use tokens for entity selection view arguments where it turns out as a major obstacle.

Proposed resolution

Process empty exception value as expected.

Remaining tasks

* Check if this is an issue in D8 and move to core then.

User interface changes

None.

API changes