[Debug] throw even in stacking mode to preserve code paths

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no if throwing a subclass is accepted
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | none

Throwing \ErrorException instead of ContextErrorException is a better work around for https://bugs.php.net/42098