Improve case when git command fails to retrieve Git tags

[dennis-behm]

Improve handling error situation in pipeline template scripts where the git tag is retrieved to compute release candidate tag:

dbb/Templates/GitlabCIPipeline/.gitlab-ci.yml

Lines 235 to 245 in bbff348

	echo [INFO] Computed tag for the next release: ${newVersionTag}
	# Compute the name of the next release candidate
	export releaseCandidate=$(git tag --list "${newVersionTag}_*rc*" --sort=version:refname | tail -n 1)
	echo [INFO] Current release candidate tag: ${releaseCandidate}
	if [ -z "${releaseCandidate}" ]; then
	# initial version tag
	export newVersionTag="${newVersionTag}_rc00"
	echo [INFO] Updated release candidate tag: ${newVersionTag}
	else