Fix a null dereference.

Change-Id: I7224c3368ff414620062bc08b80a6a94d55d7931
diff --git a/libs/gui/ISurfaceComposerClient.cpp b/libs/gui/ISurfaceComposerClient.cpp
index 1adc134..60e25c1 100644
--- a/libs/gui/ISurfaceComposerClient.cpp
+++ b/libs/gui/ISurfaceComposerClient.cpp
@@ -95,7 +95,7 @@
             status_t result = createSurface(name, w, h, format, flags,
                     &handle, &gbp);
             reply->writeStrongBinder(handle);
-            reply->writeStrongBinder(gbp->asBinder());
+            reply->writeStrongBinder(gbp != NULL ? gbp->asBinder() : NULL);
             reply->writeInt32(result);
             return NO_ERROR;
         } break;