fix: Session Update Error Handling For Youview Platform (#8918)

Fixes https://github.com/shaka-project/shaka-player/issues/8917

lib/drm/drm_engine.js

@@ -1484,11 +1484,12 @@ shaka.drm.DrmEngine = class {
       await session.update(response.data);
     } catch (error) {
       // Session update failed!
+      const errorMessage = (error && error.message) || String(error);
       const shakaErr = new shaka.util.Error(
           shaka.util.Error.Severity.CRITICAL,
           shaka.util.Error.Category.DRM,
           shaka.util.Error.Code.LICENSE_RESPONSE_REJECTED,
-          error.message);
+          errorMessage);
       this.onError_(shakaErr);
       if (metadata && metadata.updatePromise) {
         metadata.updatePromise.reject(shakaErr);