fix error if bad part name is given

.gitea/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
           maven-version: 3.8.5
 
       - name: Run Tests
-        run: mvn --batch-mode test
+        run: mvn --batch-mode test -q
 
       - name: Push to dokku
         uses: dokku/github-action@master

src/main/java/cc/fascinated/controller/PlayerController.java

@@ -47,8 +47,10 @@ public class PlayerController {
         if (player != null) { // The player exists
             Skin skin = player.getSkin();
             Skin.Parts skinPart = Skin.Parts.fromName(part);
+            if (skinPart != null) { // The part exists
                 partBytes = PlayerUtils.getSkinPartBytes(skin, skinPart, size);
             }
+        }
         if (partBytes == null) { // Fallback to the default head
             partBytes = PlayerUtils.getSkinPartBytes(Skin.DEFAULT_SKIN, Skin.Parts.HEAD, size);
         }