CallStyle: don't reglue icon+label if never glued

EmphasizedNotificationButton has two ways of rendering the icon and
label:

1. Unglued, where they're set using View's standard methods.

2. Glued, where they're saved and combined into a single Spannable with
   an ImageSpan for the icon.

A small logic error meant that we were "re-gluing" the icon and label on
layout direction updates *even if they weren't glued to start with*, and
gluing a null icon and label gives a blank button instead of the label
the caller already set.

Bug: 330746629
Test: atest NotificationEmphasizedButtonState
Flag: NA
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:7f5aea44a97747dbd699c82dea42e21369a439b4)
Merged-In: I2160dd17d39bd00a045422e2096d14b9ebb68902
Change-Id: I2160dd17d39bd00a045422e2096d14b9ebb68902