After editing the "Bug Report" form to make a minor change to its default task description template, the task form became inaccessible, both from the usage side when creating tasks, as well as from the admin side when trying to view or edit the form configuration itself.
https://phabricator.wikimedia.org/maniphest/task/edit/form/43/
https://phabricator.wikimedia.org/transactions/editengine/maniphest.task/view/43/
https://phabricator.wikimedia.org/transactions/editengine/maniphest.task/defaults/43/
These all fail with:
RuntimeException: Array to string conversion
Trace, courtesy of @Dzahn:
P30961
PHP message: [2022-07-08 03:13:12] EXCEPTION: (RuntimeException) Array to string conversion at [<arcanist>/src/error/PhutilErrorHandler.php:261] PHP message: arcanist(), ava(), phabricator(), translations(), wmf-ext-misc() PHP message: #0 <#2> PhutilErrorHandler::handleError(integer, string, string, integer, array) called at [<phabricator>/src/view/form/control/AphrontFormTextAreaControl.php:76] PHP message: #1 <#2> AphrontFormTextAreaControl::renderInput() called at [<phabricator>/src/view/form/control/PhabricatorRemarkupControl.php:390] PHP message: #2 <#2> PhabricatorRemarkupControl::renderInput() called at [<phabricator>/src/view/form/control/AphrontFormControl.php:172] PHP message: #3 <#2> phutil_tag(string, array, array) called at [<phabricator>/src/view/form/PHUIFormLayoutView.php:54] PHP message: #4 <#2> PHUIFormLayoutView::render() called at [<phabricator>/src/view/form/AphrontFormView.php:160] PHP message: #5 <#2> phutil_tag(string, array, array) called at [<phabricator>/src/infrastructure/javelin/markup.php:70] PHP message: #6 <#2> phutil_escape_html(array) called at [<phabricator>/src/infrastructure/markup/render.php:139] PHP message: #7 <#2> phutil_escape_html(array) called at [<phabricator>/src/infrastructure/markup/render.php:97] PHP message: #8 <#2> phutil_tag(string, array, array) called at [<phabricator>/src/view/phui/PHUITwoColumnView.php:203] PHP message: #9 <#2> PHUITwoColumnView::buildMainColumn() called at [<phabricator>/src/view/phui/PHUITwoColumnView.php:121] PHP message: #10 <#2> PHUITwoColumnView::getTagContent() called at [<phabricator>/src/view/AphrontTagView.php:161] PHP message: #11 <#2> AphrontTagView::render() called at [<phabricator>/src/view/AphrontView.php:222] PHP message: #12 <#2> AphrontView::producePhutilSafeHTML() called at [<phabricator>/src/infrastructure/markup/render.php:115] PHP message: #13 <#2> phutil_escape_html(PHUITwoColumnView) called at [<phabricator>/src/infrastructure/markup/render.php:171] PHP message: #14 <#2> phutil_implode_html(string, array) called at [<phabricator>/src/view/page/PhabricatorBarePageView.php:58] PHP message: #15 <#2> PhabricatorBarePageView::willRenderPage() called at [<phabricator>/src/view/page/PhabricatorStandardPageView.php:217] PHP message: #16 <#2> PhabricatorStandardPageView::willRenderPage() called at [<phabricator>/src/view/page/AphrontPageView.php:46] PHP message: #17 <#2> AphrontPageView::render() called at [<