Fix compilation with new Purpose param in ExtraCel::create()

src/app/extra_cel.h

@@ -33,6 +33,7 @@ namespace app {
       Unknown,
       BrushPreview,
       TransformationPreview,
+      TextPreview,
     };
 
     ExtraCel();

src/app/ui/editor/moving_slice_state.cpp

@@ -225,6 +225,7 @@ void MovingSliceState::drawExtraCel(int layerIdx)
     }
 
     m_extraCel->create(
+      ExtraCel::Purpose::TransformationPreview,
       m_site.tilemapMode(),
       m_site.document()->sprite(),
       bounds,

src/app/ui/editor/writing_text_state.cpp

@@ -99,6 +99,7 @@ private:
   void createExtraCel(const Site& site,
                       const gfx::Rect& bounds) {
     m_extraCel->create(
+      ExtraCel::Purpose::TextPreview,
       site.tilemapMode(),
       site.sprite(),
       bounds,