Fixed folder versioning

src/main/java/com/nutomic/syncthingandroid/fragments/FolderFragment.java

@@ -128,6 +128,7 @@ public class FolderFragment extends Fragment
                 mFolder.versioning = new Folder.Versioning();
                 mVersioningKeepView.setText(R.string.off);
             } else {
+                mFolder.versioning.type = "simple";
                 mFolder.versioning.params.put("keep", valueOf(intValue));
                 mVersioningKeepView.setText(valueOf(intValue));
             }