You guys can use a different script:
#!/bin/bash
projectFilePath=$BITRISE_SOURCE_DIR/YourProjectPath/project.pbxproj
version_number=`sed -n '/MARKETING_VERSION/{s/MARKETING_VERSION = //;s/;//;s/^[[:space:]]*//;p;q;}' $projectFilePath`
envman add --key MARKETING_VERSION_REVISED --value $version_number
Then you can use $MARKETING_VERSION_REVISED in the next workflow steps.