Fix flash of unstyled content in action view page (#24712)

# Before

![rec](https://github.com/go-gitea/gitea/assets/20454870/32f8e521-f743-4101-bd3c-923fd5abd893)

# After

![rec](https://github.com/go-gitea/gitea/assets/20454870/070721d1-6749-43c1-ac18-d8c58e5f0901)

Ref: https://github.com/go-gitea/gitea/issues/24625

Signed-off-by: Yarden Shoham <git@yardenshoham.com>
Co-authored-by: Giteabot <teabot@gitea.io>

web_src/js/components/RepoActionView.vue

@@ -19,7 +19,7 @@
       <div class="action-commit-summary">
         {{ run.commit.localeCommit }}
         <a :href="run.commit.link">{{ run.commit.shortSHA }}</a>
-        &nbsp;<span class="ui label">
+        &nbsp;<span class="ui label" v-if="run.commit.shortSHA">
           <a :href="run.commit.branch.link">{{ run.commit.branch.name }}</a>
         </span>
         &nbsp;{{ run.commit.localePushedBy }}