Fixed unused variable warning if asserts are compiled out.

imgui.cpp

@@ -2263,6 +2263,7 @@ static void AddDrawListToRenderList(ImVector<ImDrawList*>& out_render_list, ImDr
         // Check that draw_list doesn't use more vertices than indexable (default ImDrawIdx = 2 bytes = 64K vertices)
         // If this assert triggers because you are drawing lots of stuff manually, A) workaround by calling BeginChild()/EndChild() to put your draw commands in multiple draw lists, B) #define ImDrawIdx to a 'unsigned int' in imconfig.h and render accordingly.
         const unsigned long long int max_vtx_idx = (unsigned long long int)1L << (sizeof(ImDrawIdx)*8);
+        (void)max_vtx_idx;
         IM_ASSERT((unsigned long long int)draw_list->_VtxCurrentIdx <= max_vtx_idx);
 
         GImGui->IO.MetricsRenderVertices += draw_list->VtxBuffer.Size;