Pollutant: Fix db create.

src/Model/Pollutants/Pollutants.py

@@ -319,7 +319,10 @@ class Pollutants(SQLSubModel):
           )
         """)
 
-        return True
+        if ext != "":
+            return True
+
+        return cls._create_submodel(execute)
 
     @classmethod
     def _db_update(cls, execute, version, data=None):