Nav, Docking: fix dimming crash with accessing zero-cmd ImDrawList (amend 1dc3af3, 23ef6c1)

# Conflicts:
#	imgui.cpp

Author: ocornut

imgui.cpp

@@ -2476,7 +2476,7 @@ bool ImGuiListClipper::Step()
             IM_ASSERT(table->RowPosY1 == StartPosY && table->RowPosY2 == window->DC.CursorPos.y);
 
         ItemsHeight = (window->DC.CursorPos.y - StartPosY) / (float)(DisplayEnd - DisplayStart);
-        float affected_by_floating_point_precision = ImIsFloatAboveGuaranteedIntegerPrecision(StartPosY) || ImIsFloatAboveGuaranteedIntegerPrecision(window->DC.CursorPos.y);
+        bool affected_by_floating_point_precision = ImIsFloatAboveGuaranteedIntegerPrecision(StartPosY) || ImIsFloatAboveGuaranteedIntegerPrecision(window->DC.CursorPos.y);
         if (affected_by_floating_point_precision)
             ItemsHeight = window->DC.PrevLineSize.y + g.Style.ItemSpacing.y; // FIXME: Technically wouldn't allow multi-line entries.
 
@@ -4456,13 +4456,13 @@ static void ImGui::RenderDimmedBackgroundBehindWindow(ImGuiWindow* window, ImU32
     // Draw behind window by moving the draw command at the FRONT of the draw list
     {
         ImDrawList* draw_list = window->RootWindow->DrawList;
-        draw_list->AddDrawCmd();
         draw_list->PushClipRect(viewport_rect.Min - ImVec2(1, 1), viewport_rect.Max + ImVec2(1, 1), false); // Ensure ImDrawCmd are not merged
         draw_list->AddRectFilled(viewport_rect.Min, viewport_rect.Max, col);
         ImDrawCmd cmd = draw_list->CmdBuffer.back();
         IM_ASSERT(cmd.ElemCount == 6);
         draw_list->CmdBuffer.pop_back();
         draw_list->CmdBuffer.push_front(cmd);
+        draw_list->PopClipRect();
     }
 }
 
@@ -4608,6 +4608,10 @@ void ImGui::Render()
             AddDrawListToDrawData(&viewport->DrawDataBuilder.Layers[0], GetBackgroundDrawList(viewport));
     }
 
+    // Draw modal/window whitening backgrounds
+    if (first_render_of_frame)
+        RenderDimmedBackgrounds();
+
     // Add ImDrawList to render
     ImGuiWindow* windows_to_render_top_most[2];
     windows_to_render_top_most[0] = (g.NavWindowingTarget && !(g.NavWindowingTarget->Flags & ImGuiWindowFlags_NoBringToFrontOnFocus)) ? g.NavWindowingTarget->RootWindow : NULL;
@@ -4623,10 +4627,6 @@ void ImGui::Render()
         if (windows_to_render_top_most[n] && IsWindowActiveAndVisible(windows_to_render_top_most[n])) // NavWindowingTarget is always temporarily displayed as the top-most window
             AddRootWindowToDrawData(windows_to_render_top_most[n]);
 
-    // Draw modal/window whitening backgrounds
-    if (first_render_of_frame)
-        RenderDimmedBackgrounds();
-
     // Setup ImDrawData structures for end-user
     g.IO.MetricsRenderVertices = g.IO.MetricsRenderIndices = 0;
     for (int n = 0; n < g.Viewports.Size; n++)