[FIX] Align 'state' column null-guard with sibling owner/asset_type columns

Use the same falsy check (!data) as the owner/asset_type renderers
instead of a strict === null comparison, so an undefined state value
falls back to 'Unknown' instead of throwing on data.state_name.

Author: Che4ter

ui/src/pages/view.customers.js

@@ -254,7 +254,7 @@ $(document).ready(function() {
             {
                 "data": "state",
                 "render": function(data, type, row) {
-                    if (data === null) {
+                    if (!data) {
                         return 'Unknown';
                     }
                     return type === 'display' ? sanitizeHTML(data.state_name) : data.state_name;