added logic for prev/next when an instrument has no placebales associated with it
added logic for prev/next when an instrument has no placebales associated with it

OpenTrons/opentrons-api,OpenTrons/opentrons-api,Opentrons/labware,OpenTrons/opentrons-api,OpenTrons/opentrons-api,OpenTrons/opentrons_sdk,OpenTrons/opentrons-api