Fix stock-out boot, transfer 500, Clear buttons and uncaught engine errors

Return JSON from any uncaught engine exception, stop the empty stock-out warehouse list aborting page boot, reject non-transfer rows in the transfer lookup, define the missing reset_input helper, and remove a stale unreferenced copy of confirm_order.php.

app/ics/manage_stock_transfer.php

@@ -630,6 +630,12 @@
       action: 'read',
       onSuccess: function(res) {
         var data    = res.output;
+        if (!data || !data.ref) {
+          bootbox.alert('Stock transfer not found.', function() {
+            window.location.href = '<?php echo $server_url?>ics/stock_transfer.php';
+          });
+          return;
+        }
         var from_wh = data.ref.ref_warehouse;
         var to_wh   = data.ref_warehouse;