OO-1401: check if a file was uploaded before managing it

src/main/java/org/olat/commons/calendar/ui/CalendarFileUploadController.java

@@ -70,6 +70,19 @@ public class CalendarFileUploadController extends FormBasicController {
 		uifactory.addFormCancelButton("cancel", buttonsCont, ureq, getWindowControl());
 	}
 
+	@Override
+	protected boolean validateFormLogic(UserRequest ureq) {
+		boolean allOk = true;
+		
+		uploadEl.clearError();
+		if(uploadEl.getUploadFile() == null) {
+			 uploadEl.setErrorKey("form.legende.mandatory", null);
+			 allOk &= false;
+		}
+		
+		return allOk & super.validateFormLogic(ureq);
+	}
+
 	@Override
 	protected void formOK(UserRequest ureq) {
 		File uploadedFile = uploadEl.getUploadFile();