Fix release script once again (#4323)

- **PR Description**

I have no regrets about testing this script one PR at a time.

- **Please check if the PR fulfills these requirements**

* [ ] Cheatsheets are up-to-date (run `go generate ./...`)
* [ ] Code has been formatted (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#code-formatting))
* [ ] Tests have been added/updated (see
[here](https://github.com/jesseduffield/lazygit/blob/master/pkg/integration/README.md)
for the integration test guide)
* [ ] Text is internationalised (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#internationalisation))
* [ ] If a new UserConfig entry was added, make sure it can be
hot-reloaded (see
[here](https://github.com/jesseduffield/lazygit/blob/master/docs/dev/Codebase_Guide.md#using-userconfig))
* [ ] Docs have been updated if necessary
* [ ] You've read through your own file changes for silly mistakes etc

<!--
Be sure to name your PR with an imperative e.g. 'Add worktrees view'
see https://github.com/jesseduffield/lazygit/releases/tag/v0.40.0 for
examples
-->

.github/workflows/release.yml

@@ -33,6 +33,12 @@ jobs:
       - name: Get Latest Tag
         run: |
           latest_tag=$(git describe --tags $(git rev-list --tags --max-count=1) || echo "v0.0.0")
+
+          if ! [[ $latest_tag =~ ^v[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+            echo "Error: Tag format is invalid. Expected format: vX.X.X"
+            exit 1
+          fi
+
           echo "Latest tag: $latest_tag"
           echo "latest_tag=$latest_tag" >> $GITHUB_ENV
 
@@ -90,7 +96,13 @@ jobs:
             patch=0
           fi
 
-          new_tag="v$major.$minor.$patch"
+          new_tag="$major.$minor.$patch"
+
+          if ! [[ $new_tag =~ ^v[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+            echo "Error: New tag's format is invalid. Expected format: vX.X.X"
+            exit 1
+          fi
+
           echo "New tag: $new_tag"
           echo "new_tag=$new_tag" >> $GITHUB_ENV