handle case where no palette is used

embroider_print.py

@@ -377,7 +377,7 @@ class Print(InkstitchExtension):
             svg_overview = overview_svg,
             color_blocks = stitch_plan.color_blocks,
             palettes = ThreadCatalog().palette_names(),
-            selected_palette = palette.name,
+            selected_palette = palette,
         )
 
         # We've totally mucked with the SVG.  Restore it so that we can save

print/templates/ui.html

@@ -42,7 +42,7 @@
               <option value="" selected>None</option>
             {% endif %}
             {% for palette in palettes %}
-              <option value="{{ palette }}" {{ "selected" if palette == selected_palette else "" }}>{{ palette }}</option>
+              <option value="{{ palette }}" {{ "selected" if palette == selected_palette.name else "" }}>{{ palette }}</option>
             {% endfor %}
           </select>
         </p>