Bugfix for issue #220: exception on Android 4.3

tested on Android 4.3, 4.0.3 and 2.3.3

src/com/owncloud/android/providers/FileContentProvider.java

@@ -86,7 +86,7 @@ public class FileContentProvider extends ContentProvider {
     private static final UriMatcher mUriMatcher;
     static {
         mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
-        mUriMatcher.addURI(ProviderMeta.AUTHORITY_FILES, "/", ROOT_DIRECTORY);
+        mUriMatcher.addURI(ProviderMeta.AUTHORITY_FILES, null, ROOT_DIRECTORY);
         mUriMatcher.addURI(ProviderMeta.AUTHORITY_FILES, "file/", SINGLE_FILE);
         mUriMatcher.addURI(ProviderMeta.AUTHORITY_FILES, "file/#", SINGLE_FILE);
         mUriMatcher.addURI(ProviderMeta.AUTHORITY_FILES, "dir/#", DIRECTORY);