view_units: Fix find, disband and upgrade buttons

The checks whether the find, disband and upgrade buttons should be
enabled reference the wrong columns in the table.

This commit fixes the column references.

client/views/view_units.cpp

@@ -392,12 +392,12 @@ void units_view::selection_changed(const QItemSelection &sl,
     qvar = itm->data(Qt::UserRole);
     uid = qvar.toInt();
     selected = cid_decode(uid);
-    counter = ui.units_widget->item(curr_row, 3)->text().toInt();
+    counter = ui.units_widget->item(curr_row, 4)->text().toInt();
     if (counter > 0) {
       ui.disband_but->setDisabled(false);
       ui.find_but->setDisabled(false);
     }
-    upg = ui.units_widget->item(curr_row, 1)->text();
+    upg = ui.units_widget->item(curr_row, 2)->text();
     if (upg != "-") {
       ui.upg_but->setDisabled(false);
     }