skip update test when previous version is unavailable

Signed-off-by: morph027 <stefan.heitmueller@gmx.com>

.gitlab-ci/test-update.sh

@@ -4,7 +4,9 @@
 
 curl -sL -o /etc/apt/trusted.gpg.d/morph027-gitea.asc https://packaging.gitlab.io/gitea/gpg.key
 echo "deb [arch=amd64] https://packaging.gitlab.io/gitea gitea main" > /etc/apt/sources.list.d/morph027-gitea.list
-apt-get update
+if ! apt-get update; then
+    exit 0
+fi
 apt-get -y install gitea
 install -o gitea -g gitea -m 644 "/${CI_PROJECT_DIR}/.gitlab-ci/app.ini" /etc/gitea/app.ini
 start_gitea