Work around wxWidgets failure to send first key through validator. Unify treatment of INDETERMINATE values (such as for multiple selections with mixed values). (cherry picked from commit 7308729)
Fixes: lp:1676178 * https://bugs.launchpad.net/kicad/+bug/1676178 Fixes: lp:1749220 * https://bugs.launchpad.net/kicad/+bug/1749220 Fixes: lp:1779557 * https://bugs.launchpad.net/kicad/+bug/1779557 Fixes: lp:1425134 * https://bugs.launchpad.net/kicad/+bug/1425134 Fixes: lp:1565195 * https://bugs.launchpad.net/kicad/+bug/1565195 (cherry picked from commit b6aee79)