Skip window infos updates if no listeners

This change fixes a bug where WindowInfosListenerInvoker's active
message count is incremented for messages when there are no listeners.
In this case, onWindowInfosReported is never called, leading to
out-of-sync window infos once listeners are added back. This scenario
may occur if system server dies.

Bug: 279792237
Test: WindowInfosListenerInvokerTest, manual tested by killing system server
Change-Id: If62f7cc56b48570f633e8e640006f020b053ea6f
Merged-In: If62f7cc56b48570f633e8e640006f020b053ea6f