Passing an invalid index gives an assertion in debug mode and crashes in
release mode due to an out-of-bounds access. Fix it by appending the
given widget (same as passing a negative index which is documented).
Pick-to: 6.5 6.2
Fixes: QTBUG-130275
Change-Id: Id0c245e185acc36e5d07cea1d22619bb0e9eee07
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
(cherry picked from commit 0f9062ec71021c256dba7ee8498f036d7aac0821)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 3c0f08ab7064d2c4183844613f08b3630f180fef)
f70803eefb