Don't try to delete paths that don't exist

PiperOrigin-RevId: 506905444
Change-Id: I6dc676d6e41a2dd5e6bb80a1c92d8927906a0ee2

Author: joshgoldman-google

java/com/google/copybara/CheckoutPath.java

@@ -242,6 +242,9 @@ public void remove() throws ValidationException, EvalException {
       })
   public void rmDir(boolean recursive) throws ValidationException, EvalException {
     try {
+      if (!Files.exists(checkoutDir.resolve(path))) {
+        return;
+      }
       if (recursive) {
         FileUtil.deleteRecursively(checkoutDir.resolve(path));
       } else {