Make sure to noop when there is no DSN (#1852)

* Make sure to noop when there is no or invalid DSN

Author: antonpirker

sentry_sdk/integrations/opentelemetry/span_processor.py

@@ -98,6 +98,14 @@ def on_start(self, otel_span, parent_context=None):
         if not hub:
             return
 
+        if not hub.client or (hub.client and not hub.client.dsn):
+            return
+
+        try:
+            _ = Dsn(hub.client.dsn or "")
+        except Exception:
+            return
+
         if hub.client and hub.client.options["instrumenter"] != INSTRUMENTER.OTEL:
             return