Assertion failure on invalid view in write trace

When I attempt to call dump on a view reference from within a write trace callback and the view variable has an invalid value, then I get an assertion failure.

 test 1 {invalid view in write trace} {
    set ::result {}
    trace add variable w write dumpw
    proc dumpw args {lappend ::result [view @w dump]}
    set error [catch {set w sometext} msg]
    trace remove variable w write dumpw
    rename dumpw {}
    set error
 } 1

 Failed assertion at src_tcl/viewobj.c, line 117: o != NULL