Shader: Fix unit tests

include/Nazara/Shader/Ast/Attribute.hpp

@@ -39,6 +39,8 @@ namespace Nz::ShaderAst
 
 			bool HasValue() const;
 
+			void Reset();
+
 			ExpressionValue& operator=(const ExpressionValue&) = default;
 			ExpressionValue& operator=(ExpressionValue&&) noexcept = default;
 

include/Nazara/Shader/Ast/Attribute.inl

@@ -67,6 +67,12 @@ namespace Nz::ShaderAst
 	{
 		return !std::holds_alternative<std::monostate>(m_value);
 	}
+
+	template<typename T>
+	void ExpressionValue<T>::Reset()
+	{
+		m_value = {};
+	}
 }
 
 #include <Nazara/Shader/DebugOff.hpp>