Situation

Unable to create pre-release with an empty token.

To Reproduce

Run this script:

ver = semver.VersionInfo.parse('1.0.0')
ver = ver.bump_prerelease('');
print(ver)
# 1.0.0-rc.1

Expected Behavior

.bump_prerelease('') should generate an version like 1.0.0-1.

Environment

• OS: Linux ubuntu 5.11.0-40-generic
• Python version: Docker image python:3.8
• Version of semver library: semver==2.13.0

Additional context

Pre-release documentation https://semver.org/#spec-item-9