Improved perf when focusing on Palette mode for the first time

Author: 0x5bfa

src/Files.App/ViewModels/UserControls/NavigationToolbarViewModel.cs

@@ -243,7 +243,8 @@ public  bool IsOmnibarFocused
 								_ = PopulateOmnibarSuggestionsForPathMode();
 								break;
 							case OmnibarPaletteModeName:
-								PopulateOmnibarSuggestionsForCommandPaletteMode();
+								if (OmnibarCommandPaletteModeSuggestionItems.Count is 0)
+									PopulateOmnibarSuggestionsForCommandPaletteMode();
 								break;
 							case OmnibarSearchModeName:
 								break;