handle "null" in "timepicker:quickRanges" migration (#95767) (#96317)

# Conflicts:
#	src/core/server/ui_settings/saved_objects/migrations.test.ts

Author: Dosant

src/core/server/ui_settings/saved_objects/migrations.test.ts

@@ -44,3 +44,53 @@ describe('ui_settings 7.9.0 migrations', () => {
     });
   });
 });
+
+describe('ui_settings 7.12.0 migrations', () => {
+  const migration = migrations['7.12.0'];
+
+  test('returns doc on empty object', () => {
+    expect(migration({} as SavedObjectUnsanitizedDoc)).toEqual({
+      references: [],
+    });
+  });
+  test('properly migrates timepicker:quickRanges', () => {
+    const initialQuickRange: any = {
+      from: '123',
+      to: '321',
+      display: 'abc',
+      section: 2,
+    };
+    const { section, ...migratedQuickRange } = initialQuickRange;
+
+    const doc = {
+      type: 'config',
+      id: '8.0.0',
+      attributes: {
+        buildNum: 9007199254740991,
+        'timepicker:quickRanges': JSON.stringify([initialQuickRange]),
+      },
+      references: [],
+      updated_at: '2020-06-09T20:18:20.349Z',
+      migrationVersion: {},
+    };
+    const migrated = migration(doc);
+    expect(JSON.parse(migrated.attributes['timepicker:quickRanges'])).toEqual([migratedQuickRange]);
+  });
+
+  // https://github.com/elastic/kibana/issues/95616
+  test('returns doc when "timepicker:quickRanges" is null', () => {
+    const doc = {
+      type: 'config',
+      id: '8.0.0',
+      attributes: {
+        buildNum: 9007199254740991,
+        'timepicker:quickRanges': null,
+      },
+      references: [],
+      updated_at: '2020-06-09T20:18:20.349Z',
+      migrationVersion: {},
+    };
+    const migrated = migration(doc);
+    expect(migrated).toEqual(doc);
+  });
+});

src/core/server/ui_settings/saved_objects/migrations.ts

@@ -32,7 +32,7 @@ export const migrations = {
     ...doc,
     ...(doc.attributes && {
       attributes: Object.keys(doc.attributes).reduce((acc, key) => {
-        if (key === 'timepicker:quickRanges' && doc.attributes[key].indexOf('section') > -1) {
+        if (key === 'timepicker:quickRanges' && doc.attributes[key]?.indexOf('section') > -1) {
           const ranges = JSON.parse(doc.attributes[key]).map(
             ({ from, to, display }: { from: string; to: string; display: string }) => {
               return {