Fixed palette browser crash and loading when importing from lospec

src/PixiEditor/ViewModels/SubViewModels/ColorsViewModel.cs

@@ -201,6 +201,7 @@ internal class ColorsViewModel : SubViewModel<ViewModelMain>, IColorsHandler
                     }
                 }
 
+                browser.IsFetching = false;
                 await SavePalette(palette, browser);
             }
             else

src/PixiEditor/Views/Windows/PalettesBrowser.axaml.cs

@@ -344,6 +344,11 @@ internal partial class PalettesBrowser : PixiEditorPopup, IPopupWindow
         {
             SortedResults.Add(updatedItem);
         }
+        
+        if(PaletteList == null)
+        {
+            PaletteList = new PaletteList();
+        }
 
         if(!PaletteEquals(updatedItem, PaletteList.Palettes))
         {