Fix sweep step for tainted QObject JavaScript wrappers

Merged Nate Graham requested to merge ngraham/qtdeclarative:vladpatch into kde/5.15


Currently, whenever the garbage collector runs, it will destroy all
valid tainted wrappers.

Only null or undefined wrappers will be preserved in the
m_multiplyWrappedQObjects map.

It seems like "!" was overlooked in
3b5d37ce3841c4bfdf1c629d33f0e33b881b47fb. Prior to that change, it
was "!it.value()->markBit()", so calling erase() in the then branch
did make sense. But with "!it.value().isNullOrUndefined()", erase()
will be called for every valid wrapper, which is the opposite what we

Pick-to: 5.15 6.2
Change-Id: I2bf2630f538af8cbd4bfffcff29d67be6c278265
Reviewed-by: Fabian Kosmale <>
(cherry picked from commit e6b2f88d892dcf396580a61662f569bf69d6d9d1)
Edited by Nate Graham

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