OrcLib: Utils: DescriptorGuard: fix operator* calling copy ctor

Author: fabienfl-orc

src/OrcLib/Utils/Guard.h

@@ -166,6 +166,7 @@ class DescriptorGuard
     T& value() { return m_data; }
 
     const T& operator*() const { return m_data; }
+    T& operator*() { return m_data; }
 
     T* data() { return &m_data; }
     const T* data() const { return &m_data; }