Merge pull request #3 from shimo-react-native/fix/nullpoint-bug-1

Update RNFetchBlobFS.java

Author: wsong910

android/src/main/java/com/RNFetchBlob/RNFetchBlobFS.java

@@ -215,7 +215,13 @@ static public Map<String, Object> getSystemfolders(ReactApplicationContext ctx)
         state = Environment.getExternalStorageState();
         if (state.equals(Environment.MEDIA_MOUNTED)) {
             res.put("SDCardDir", Environment.getExternalStorageDirectory().getAbsolutePath());
-            res.put("SDCardApplicationDir", ctx.getExternalFilesDir(null).getParentFile().getAbsolutePath());
+            final File externalFilesDir = ctx.getExternalFilesDir(null);
+            if (externalFilesDir != null) {
+                final File parentFile = externalFilesDir.getParentFile();
+                if (parentFile != null) {
+                    res.put("SDCardApplicationDir", parentFile.getAbsolutePath());
+                }
+            }
         }
         res.put("MainBundleDir", ctx.getApplicationInfo().dataDir);
         return res;