Update Sketch.java

This should fix the build error

Author: timkoers

arduino-core/src/processing/app/Sketch.java

@@ -9,6 +9,7 @@
 
 import cc.arduino.files.DeleteFilesOnShutdown;
 import processing.app.helpers.FileUtils;
+import processing.app.EditorTab;
 
 import static processing.app.I18n.tr;