TreeNode: removed TreeLinesSize > 0.0f optimization check. (#2920)

This is desirable but we'd need to avoid exposing 0.0f in style editor + assert on it.

imgui_demo.cpp

@@ -8286,7 +8286,7 @@ void ImGui::ShowStyleEditor(ImGuiStyle* ref)
                         style.TreeLinesFlags = option;
                 ImGui::EndCombo();
             }
-            ImGui::SliderFloat("TreeLinesSize", &style.TreeLinesSize, 0.0f, 1.0f, "%.0f");
+            ImGui::SliderFloat("TreeLinesSize", &style.TreeLinesSize, 0.0f, 2.0f, "%.0f");
             ImGui::Combo("ColorButtonPosition", (int*)&style.ColorButtonPosition, "Left\0Right\0");
             ImGui::SliderFloat2("ButtonTextAlign", (float*)&style.ButtonTextAlign, 0.0f, 1.0f, "%.2f");
             ImGui::SameLine(); HelpMarker("Alignment applies when a button is larger than its text content.");

imgui_widgets.cpp

@@ -6641,7 +6641,7 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
     bool store_tree_node_stack_data = false;
     if ((flags & ImGuiTreeNodeFlags_DrawLinesMask_) == 0)
         flags |= g.Style.TreeLinesFlags;
-    const bool draw_tree_lines = (flags & (ImGuiTreeNodeFlags_DrawLinesFull | ImGuiTreeNodeFlags_DrawLinesToNodes)) && (frame_bb.Min.y < window->ClipRect.Max.y);// && (g.Style.TreeLinesSize > 0.0f);
+    const bool draw_tree_lines = (flags & (ImGuiTreeNodeFlags_DrawLinesFull | ImGuiTreeNodeFlags_DrawLinesToNodes)) && (frame_bb.Min.y < window->ClipRect.Max.y) && (g.Style.TreeLinesSize > 0.0f);
     if (is_open && !(flags & ImGuiTreeNodeFlags_NoTreePushOnOpen))
     {
         if ((flags & ImGuiTreeNodeFlags_NavLeftJumpsBackHere) && !g.NavIdIsAlive)