Fix bug of tag_version_prefix is empty

`git tag 0.0.1` and `tag_version_prefix: ""` will trigger this bug.
`${INPUT_TAG_VERSION_PREFIX:-v}` will return 'v' when `$INPUT_TAG_VERSION_PREFIX` is ""

Author: Freed-Wu

entrypoint.sh

@@ -2,7 +2,8 @@
 
 set -o errexit -o pipefail -o nounset
 
-NEW_RELEASE=${GITHUB_REF##*/${INPUT_TAG_VERSION_PREFIX:-v}}
+NEW_RELEASE=${GITHUB_REF#refs/tags/}
+NEW_RELEASE=${NEW_RELEASE#${INPUT_TAG_VERSION_PREFIX:-v}}
 
 export HOME=/home/builder