SpongeVanilla integration and JSON check fix

minecraft-server/start-minecraftFinalSetup

@@ -24,12 +24,17 @@ if [ -n "$ICON" -a ! -e server-icon.png ]; then
 fi
 
 # Make sure files exist and are valid JSON (for pre-1.12 to 1.12 upgrades)
-for j in *.json; do
-  if [[ $(python -c "print open('$j').read().strip()==''") = True ]]; then
-    echo "Fixing JSON $j"
-    echo '[]' > $j
-  fi
-done
+if [[ -z "ls *.json" ]]; then
+  echo "Checking JSON files"
+  for j in *.json; do
+    if [[ $(python -c "print open('$j').read().strip()==''") = True ]]; then
+      echo "Fixing JSON $j"
+      echo '[]' > $j
+    fi
+  done
+else
+  echo "Skipping JSON check. No files present."
+fi
 
 # If any modules have been provided, copy them over
 mkdir -p /data/mods