fix(spp_statistic): fix unreachable privacy service delegation

Empty recordsets in Odoo are falsy, so checking `if privacy_service:`
would always evaluate to False even when the model is installed.
Changed to `if privacy_service is not None:` to correctly detect
when the spp.metrics.privacy model is available.

Author: jeremi

spp_statistic/models/statistic.py

@@ -267,7 +267,7 @@ def apply_suppression(self, value, count=None, context=None):
 
         # Delegate to unified privacy service
         privacy_service = self.env.get("spp.metrics.privacy")
-        if privacy_service:
+        if privacy_service is not None:
             stat_config = {"minimum_count": min_count, "suppression_display": display_mode}
             return privacy_service.suppress_value(value, count, stat_config=stat_config)