check for missing filename (needs to be specified when tool is launched)



git-svn-id: http://skia.googlecode.com/svn/trunk@1287 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/bench/DecodeBench.cpp b/bench/DecodeBench.cpp
index 6abd054..ac11089 100644
--- a/bench/DecodeBench.cpp
+++ b/bench/DecodeBench.cpp
@@ -33,10 +33,12 @@
     }
 
     virtual void onDraw(SkCanvas* canvas) {
-        for (int i = 0; i < N; i++) {
-            SkBitmap bm;
-            SkImageDecoder::DecodeFile(fFilename, &bm, fPrefConfig,
-                                       SkImageDecoder::kDecodePixels_Mode);
+        if (fFilename) {
+            for (int i = 0; i < N; i++) {
+                SkBitmap bm;
+                SkImageDecoder::DecodeFile(fFilename, &bm, fPrefConfig,
+                                           SkImageDecoder::kDecodePixels_Mode);
+            }
         }
     }