check for null-device in iterator



git-svn-id: http://skia.googlecode.com/svn/trunk@3251 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 034486d..6e061c2 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -232,8 +232,8 @@
             }
         }
 
-        if (NULL != fCurrLayer) {
-            const DeviceCM* rec = fCurrLayer;
+        const DeviceCM* rec = fCurrLayer;
+        if (rec && rec->fDevice) {
 
             fMatrix = rec->fMatrix;
             fClip   = &((SkRasterClip*)&rec->fClip)->forceGetBW();