Given: ``` <div class="s1" [class]="null" [ngClass]="exp"> ``` Notice that `[class]` binding is not a `string`. As a result the existing logic would not concatenate `[class]` with `class="s1"`. The resulting falsy value would than be sent to `ngClass` which would promptly clear all styles on the `<div>` The new logic correctly handles falsy values for `[class]` bindings. Fix #35335 PR Close #35350