Read xml event failed: IllFormed

[bnyu]

flamegraph-flamegraph 0.6.12
#421 fixed, But I still get (on macos)

Target app exited, ending recording...
Recording completed. Saving output file...
Output file saved as: cargo-flamegraph.trace
Error: unable to collapse generated profile data

Caused by:
    Read xml event failed: IllFormed(MismatchedEndTag { expected: "frame", found: "backtrace" })

[djc]

I won't be able to look into it, but happy to review a PR.