Correcting error "ContextErrorException: Warning: call_user_func() expec...

Correcting error "ContextErrorException: Warning: call_user_func() expects parameter 1 to be a valid callback, array must have exactly two members in /src/vendor/symfony/symfony/src/Symfony/Component/EventDispatcher/EventDispatcher.php line 164"

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| Refs tickets  |
| License       | MIT
| Doc PR        |