UserAgent giving NPE (#19481)

* Adding null check for userAgent * Change files * Update packages/merge-styles/src/getVendorSettings.ts Using optional chaining instead of ternary Co-authored-by: David Zearing <dzearing@microsoft.com> Co-authored-by: Arushi Jain <arujain@microsoft.com> Co-authored-by: David Zearing <dzearing@microsoft.com>
microsoft · Aug 24, 2021 · e6ee3ff · e6ee3ff
1 parent 00df799
commit e6ee3ff
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diff --git a/change/@fluentui-merge-styles-0da7bc43-803f-44ac-9388-46a8fe7cc4a3.json b/change/@fluentui-merge-styles-0da7bc43-803f-44ac-9388-46a8fe7cc4a3.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "getVendorSettings.js file was leading to app crash if userAgent was null. Have added a null check for userAgent",
+  "packageName": "@fluentui/merge-styles",
+  "email": "arujain@microsoft.com",
+  "dependentChangeType": "patch"
+}
diff --git a/packages/merge-styles/src/getVendorSettings.ts b/packages/merge-styles/src/getVendorSettings.ts
@@ -11,7 +11,7 @@ export function getVendorSettings(): IVendorSettings {
   if (!_vendorSettings) {
     const doc = typeof document !== 'undefined' ? document : undefined;
     const nav = typeof navigator !== 'undefined' ? navigator : undefined;
-    const userAgent = nav ? nav.userAgent.toLowerCase() : undefined;
+    const userAgent = nav?.userAgent?.toLowerCase();
 
     if (!doc) {
       _vendorSettings = {