Why am I getting error "Unable to initialize workflow information: Ignoring unknown index 'iop'" using the Field Extractor with only one index?

HI All, We can't use "Field Extractor" with only one index: We always receive the same error: "Unable to initialize workflow information: Ignoring unknown index 'iop')" Stacktrace: Traceback (most recent call last): File "", line 397, in initInfoFromWorkflow File "", line 494, in setCurrentIndex ModelException: Ignoring unknown index 'iop' Could you help to fix this? Thank you so much and have a great day,