Increment iterator on early-out too

Bug: 6860046
Change-Id: I82f9e4062cb58d5479c9d8dc5f2f0770a1dcc605
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 693f241..840222c 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1162,6 +1162,7 @@
                         // guaranteed the FB is already cleared
                         layer->clearWithOpenGL(hw, clip);
                     }
+                    ++cur;
                     continue;
                 }
                 // render the layer