Fixed more fuzzer issues

src/effects/SkDisplacementMapEffect.cpp

Index: src/effects/SkDisplacementMapEffect.cpp
diff --git a/src/effects/SkDisplacementMapEffect.cpp b/src/effects/SkDisplacementMapEffect.cpp
index f43287c4d7fcfaa0a3bc9c949a7c78a2f74e1ad6..8fc4c86ec5bad966a3407c81f0cdadd233a56b90 100644
--- a/src/effects/SkDisplacementMapEffect.cpp
+++ b/src/effects/SkDisplacementMapEffect.cpp
@@ -188,7 +188,7 @@ bool SkDisplacementMapEffect::onFilterImage(Proxy* proxy,
     SkImageFilter* displacementInput = getDisplacementInput();
     SkASSERT(NULL != displacementInput);
     if ((colorInput && !colorInput->filterImage(proxy, src, ctm, &color, offset)) ||
-        !displacementInput->filterImage(proxy, src, ctm, &displ, offset)) {
+        !displacementInput || !displacementInput->filterImage(proxy, src, ctm, &displ, offset)) {

[Stephen White, 2013/12/18 00:01:14]

I don't think it should abort on a NULL displacementInput. All NULL inputs
should just default to the source bitmap.

i.e., SkBitmap displ = src, color = src;

...

displacementInput && !displacementInput->filterImage(...)
  return false;

         return false;
     }
     if ((displ.config() != SkBitmap::kARGB_8888_Config) ||