message: Fix incorrect backcolorPick button state after cancellation
diff: @@ -3704,7 +3704,10 @@ void TextureViewer::on_backcolorPick_clicked()
  QColor col = QColorDialog::getColor(Qt::black, this, tr("Choose background colour"));
  if(!col.isValid())
  + {
  + ui->backcolorPick->setChecked(!ui->checkerBack->isChecked());
  return;
  + }
  col = col.toRgb();
  m_TexDisplay.backgroundColor = FloatVector(col.redF(), col.greenF(), col.blueF(), 1.0f);
  