fix unbound variable

Author: oesteban

docker/files/run_examples.sh

@@ -16,7 +16,7 @@ echo "utils_level = DEBUG" >> ${HOME}/.nipype/nipype.cfg
 echo "log_to_file = true" >> ${HOME}/.nipype/nipype.cfg
 echo "log_directory = ${WORKDIR}/logs/example_${example_id}" >> ${HOME}/.nipype/nipype.cfg
 
-if [[ "${NIPYPE_RESOURCE_MONITOR}" == "1" ]]; then
+if [[ "${NIPYPE_RESOURCE_MONITOR:-0}" == "1" ]]; then
     echo '[execution]' >> ${HOME}/.nipype/nipype.cfg
     echo 'resource_monitor = true' >> ${HOME}/.nipype/nipype.cfg
 fi