audioflinger: Fix crash on patch creation attempt

The code for clearing software patch connections was missing
a check for a null track pointer.

Bug: 126789266
Bug: 128269566
Test: see repro steps in b/128269566
Change-Id: Ice6887622d5fa2fa3198ce15146bff3cb05f7451
diff --git a/services/audioflinger/PatchPanel.h b/services/audioflinger/PatchPanel.h
index aba2cc2..181e27c 100644
--- a/services/audioflinger/PatchPanel.h
+++ b/services/audioflinger/PatchPanel.h
@@ -128,6 +128,7 @@
             mThread->addPatchTrack(mTrack);
             mTrack->setPeerProxy(peer, true /* holdReference */);
         }
+        void clearTrackPeer() { if (mTrack) mTrack->clearPeerProxy(); }
         void stopTrack() { if (mTrack) mTrack->stop(); }
 
         void swap(Endpoint &other) noexcept {