Prevent a crash when constructing NSSL.

The dependent change was validated on qt-dev and rvc-dev, but not explicitly on qt-qpr1-dev.
 - In qt-dev, we didn't have this check that the footer view was initialized, but hasActiveClearableNotifications did not call into the mDynamicPrivacyController (it didn't exist), so there was no initialization-time NPE.
 - In rvc-dev this footer view check existed, so updateFooter never did any work until setFooterView was called, which is strictly after mDynamicPrivacyController is initialized, so there was no crash.
 - In qt-qpr1-dev, mDynamicPrivacyController was added and is checked within updateFooter, but updateFooter didn't have the view check to short circuit before doing that on initialization.

Bug: 193149550
Fixes: 206344625
Test: manually run qt-qpr1-dev with and without fix
Depends-On: I49e2b8bcec7b2ce0a9776ff30a64c07f24949da7
Change-Id: If6e99b5fbe3d2a9d9274223c35d23c30f5524229