Fix chart release CI issue (#9684)

**Description**
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Please include a summary of the change and which issue is fixed. Please
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⚒️ Fixes  # <!--(issue)-->

Fixes issue causing chart release CI to fail due to non existent
directory.

**⚙️ Type of change**

- [ ] ⚙️ Feature/App addition
- [x] 🪛 Bugfix
- [ ] ⚠️ Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] 🔃 Refactor of current code

**🧪 How Has This Been Tested?**
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**📃 Notes:**
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**✔️ Checklist:**

- [x] ⚖️ My code follows the style guidelines of this project
- [x] 👀 I have performed a self-review of my own code
- [ ] #️⃣ I have commented my code, particularly in hard-to-understand
areas
- [ ] 📄 I have made corresponding changes to the documentation
- [x] ⚠️ My changes generate no new warnings
- [ ] 🧪 I have added tests to this description that prove my fix is
effective or that my feature works
- [ ] ⬆️ I increased versions for any altered app according to semantic
versioning

**➕ App addition**

If this PR is an app addition please make sure you have done the
following.

- [ ] 🪞 I have opened a PR on
[truecharts/containers](https://github.com/truecharts/containers) adding
the container to TrueCharts mirror repo.
- [ ] 🖼️ I have added an icon in the Chart's root directory called
`icon.png`

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.github/scripts/build-catalog.sh

@@ -77,7 +77,9 @@ patch_apps() {
     cat ${target}/Chart.yaml | yq '.annotations."truecharts.org/catagories"' -r >> catalog/${train}/${chartname}/item.yaml
 
     # Generate screenshots
-    screenshots=$(ls ${target}/screenshots)
+    if [[ -d "${target}/screenshots" ]]; then
+        screenshots=$(ls ${target}/screenshots)
+    fi
     if [[ -n $screenshots ]]; then
         echo "screenshots:" >> catalog/${train}/${chartname}/item.yaml
         for screenshot in $screenshots; do