fix warning in glm

include/glm/detail/type_mat4x3.inl

@@ -56,7 +56,7 @@ namespace detail
 		size_type i
 	) const
 	{
-		assert(i < this->length());
+        assert(static_cast<length_t>(i) < this->length());
 		return this->value[i];
 	}