[NaCl SDK] nacl_io: Fix bug in Path::Range introduced in recent change.

native_client_sdk/src/libraries/nacl_io/path.cc

Index: native_client_sdk/src/libraries/nacl_io/path.cc
diff --git a/native_client_sdk/src/libraries/nacl_io/path.cc b/native_client_sdk/src/libraries/nacl_io/path.cc
index 21965607911902157416e8870a35ba24650c4e78..e75f0683831cd8bef5ec73c6f45ca93fc085866d 100644
--- a/native_client_sdk/src/libraries/nacl_io/path.cc
+++ b/native_client_sdk/src/libraries/nacl_io/path.cc
@@ -170,7 +170,7 @@ std::string Path::Range(size_t start, size_t end) const {
     }
   }
 
-  if (pstart > pend)
+  if (slashes < start || pstart > pend)
     return std::string();
 
   return std::string(pstart, pend - pstart);