Fix loop in SF flushTransactionQueues

Bug: 132594932
Test: build, boot
Change-Id: I2598a6329b6ad70cbee9418a922961b6c9b1f8f8
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index f8745f7..13b9238 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -3556,7 +3556,7 @@
                 it = mTransactionQueues.erase(it);
                 mTransactionCV.broadcast();
             } else {
-                std::next(it, 1);
+                it = std::next(it, 1);
             }
         }
     }