#2502 entry -validate set to none incorrectly

[Joe Mistachkin]

#
# This bug MAY be related to bug 1520118.
#
# This should be the minimal test script to repro
# the problem:
#
set foo ""

pack [entry .foo -validate key -validatecommand [list regexp -- {^[A-Z]*$} %P] -textvariable ::foo]

bind . <F1> [list doStuff]
bind . <F2> [list .foo configure -show ""]

proc doStuff {} {
set ::foo "ABCD "; # <-- has invalid chars
.foo configure -show *
}

[Donal K. Fellows]

I can't remember if this is correct for validation or not; I try very hard to avoid changing values when using validation (and in fact only ever use validation to drive GUI hints, not actual failure).