log an error when dequeueBuffer gets a NULL Fence

Bug: 9858745
Change-Id: If35d6a7d770bf0a42d55bc55880a9ddb721fcfd0
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index 94f21b6..bad4138 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -653,7 +653,7 @@
         mHaveBuffer = false;
     }
 
-    status_t err = s->captureScreen(display,cpuConsumer->getBufferQueue(),
+    status_t err = s->captureScreen(display, cpuConsumer->getBufferQueue(),
             reqWidth, reqHeight, minLayerZ, maxLayerZ, true);
 
     if (err == NO_ERROR) {