Watch isn't checking for mounted in post frame callback.

[RsMan-Dev]

Hi! i faced a problem in flutter today. your Watch uses a post frame callback, this is not an issue in majority of cases, but i'm using a context that is building my page twice in one frame, the first one get instantly disposed (actually an issue, but not necessarily one in other projects). so when my render finishes, watch calls an update on disposed widgets.

i made my own class to wait:
this.createComputed(() => widget.builder(context),
debugLabel: widget.debugLabel)
became:
this.createComputed(() => mounted ? widget.builder(context) : Container(),
debugLabel: widget.debugLabel)

and
WidgetsBinding.instance.addPostFrameCallback(() {
result.recompute();
if (mounted) setState(() {});
});
became
WidgetsBinding.instance.addPostFrameCallback(() {
if (mounted) result.recompute();
if (mounted) setState(() {});
});

[rodydavis]

Can you test on v6? It should be fixed.

Also please share a minimal code sample to reproduce as that is something we definitely want to test for.