Add cache clearing function and invoke on startup

api.js

@@ -15,8 +15,20 @@ if (!fs.existsSync(CACHE_DIR)) {
 
 app.use(express.json());
 
+function normalizeConfig(config) {
+    // Remove null, undefined, and empty string values
+    const normalized = {};
+    for (const [key, value] of Object.entries(config)) {
+        if (value !== null && value !== undefined && value !== '') {
+            normalized[key] = value;
+        }
+    }
+    return normalized;
+}
+
 function hashConfig(config) {
-    const configString = JSON.stringify(config);
+    const normalized = normalizeConfig(config);
+    const configString = JSON.stringify(normalized);
     return crypto.createHash('sha256').update(configString).digest('hex');
 }
 
@@ -137,7 +149,7 @@ app.get('/generate', async (req, res) => {
         const config = {
             displayName: req.query.displayName || "Anonymous",
             username: req.query.username || "@anonymous",
-            avatarUrl: req.query.avatarUrl || "",
+            avatarUrl: req.query.avatarUrl || null,
             text: req.query.text || "No text provided",
             imageUrl: req.query.imageUrl || null,
             timestamp: timestamp,
@@ -172,7 +184,7 @@ app.post('/generate', async (req, res) => {
         const config = {
             displayName: req.body.displayName || "Anonymous",
             username: req.body.username || "@anonymous",
-            avatarUrl: req.body.avatarUrl || "",
+            avatarUrl: req.body.avatarUrl || null,
             text: req.body.text || "No text provided",
             imageUrl: req.body.imageUrl || null,
             timestamp: timestamp,