[Debug] simplify code path to remove potential blank pages
bug #11097 [Debug] simplify code path to remove potential blank pages (nicolas-grekas)

This PR was merged into the 2.5 branch.

Discussion
----------

[Debug] simplify code path to remove potential blank pages

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8703
| License       | MIT
| Doc PR        | none

This should reduce the probability of hitting #8703 by removing an ob_start() from the error page output code path at bootstrap.

Commits
-------

ecefccd [Debug] simplify code path to remove potential blank pages