fix(prejoin): Don't overwrite display name with ''

react/features/base/jwt/functions.js

 export function getJwtName(state: Object) {
     const { user } = state['features/base/jwt'];
 
-    return user?.name || '';
+    return user?.name;
 }

react/features/base/settings/middleware.js

     if (hasJwt) {
         const displayName = getJwtName(state);
 
-        dispatch(updateSettings({
-            displayName
-        }));
+        if (displayName) {
+            dispatch(updateSettings({
+                displayName
+            }));
+        }
     }
 }