Keep tab variable valid in url to allow old saved/shared url to work properly

src/routes/+page.svelte

@@ -12,6 +12,7 @@
     cleanAudit,
     auditFunction,
     auditOptions,
+    auditSetValue,
   } from "@auditors/core"
   import type { PopulationWithoutId } from "@openfisca/json-model"
   import * as htmlToImage from "html-to-image"
@@ -317,6 +318,16 @@
       remainingKeys,
       auditQuerySingleton(auditTrimString),
     )
+    // Obsolete parameter must be ignored, but kept as valid in URL to prevent old url from returning wrong page
+    audit.attribute(
+      data,
+      "tab",
+      true,
+      errors,
+      remainingKeys,
+      auditQuerySingleton(auditTrimString),
+      auditSetValue(null),
+    )
     audit.attribute(
       data,
       "test_case",