Add blur to backdrop, set min-height error message

assets/postcode_modal.css

@@ -45,6 +45,11 @@
     }
 
     &::backdrop {
+        backdrop-filter: blur(2px);
         background-color: hsl(40deg 100 30 /0.5);
     }
+
+    .error_message_modal_postcode {
+        min-height: 1lh;
+    }
 }