Avoid stop current running ML worker until exit

app.py

@@ -47,6 +47,7 @@ def read_status():
 def run_ml_worker(url, api_key, hf_token):
     global ml_worker, previous_url
     previous_url = url
+    subprocess.run(["giskard", "worker", "stop"])
     ml_worker = subprocess.Popen(
         [
             "giskard", "worker", "start",
@@ -74,6 +75,9 @@ def start_ml_worker(url, api_key, hf_token):
     if not url or len(url) < 1:
         return "Please provide URL of Giskard"
 
+    if ml_worker is not None:
+        return f"ML worker is still running for {previous_url}"
+
     # Always run an external ML worker
     stop_ml_worker()