FP4T-438  [Monkey][Crash] com.android.wallpaper

* Root Cause
  Null pointer protection
* Solution
  GC may have reclaimed the inputStream object.
* Test Steps
  Monkey Not Test
* Test Result
  pass

Change-Id: I5942af09a951db09b33808ad45ef73be4503b47c
diff --git a/src/com/android/wallpaper/asset/StreamableAsset.java b/src/com/android/wallpaper/asset/StreamableAsset.java
index 80e02cd..cd4c015 100755
--- a/src/com/android/wallpaper/asset/StreamableAsset.java
+++ b/src/com/android/wallpaper/asset/StreamableAsset.java
@@ -306,7 +306,9 @@
      */
     private void closeInputStream(InputStream inputStream, String errorMessage) {
         try {
-            inputStream.close();
+            if (inputStream != null) {
+                inputStream.close();
+            }
         } catch (IOException e) {
             Log.e(TAG, errorMessage);
         }