tools: set correct icon for dialogs

tools/level_editor/level_editor.vala

@@ -419,7 +419,6 @@ public class LevelEditorApplication : Gtk.Application
 
 		// Widgets
 		_preferences_dialog = new PreferencesDialog(this);
-		_preferences_dialog.set_icon_name(CROWN_ICON_NAME);
 		_preferences_dialog.delete_event.connect(() => { _preferences_dialog.hide(); return Gdk.EVENT_STOP; });
 
 		_combo = new Gtk.ComboBoxText();

tools/level_editor/preferences_dialog.vala

@@ -39,6 +39,7 @@ public class PreferencesDialog : Gtk.Dialog
 	{
 		this.title = "Preferences";
 		this.border_width = 0;
+		this.set_icon_name(CROWN_ICON_NAME);
 
 		// Data
 		_application = app;

tools/level_editor/sprite_import_dialog.vala

@@ -130,6 +130,7 @@ public class SpriteImportDialog : Gtk.Dialog
 	{
 		this.border_width = 4;
 		this.title = "Import Sprite...";
+		this.set_icon_name(CROWN_ICON_NAME);
 
 		try
 		{