For backend-specific observers, filter out deployments without backend
types set
diff --git a/planetstack/core/models/site.py b/planetstack/core/models/site.py
index 9f183b5..0ade5df 100644
--- a/planetstack/core/models/site.py
+++ b/planetstack/core/models/site.py
@@ -20,7 +20,7 @@
 
         parent_queryset = parent.get_queryset() if hasattr(parent, "get_queryset") else parent.get_query_set()
         if (backend_type):
-            return parent_queryset.filter(Q(deployment__backend_type=backend_type)|Q(backend_type=None))
+            return parent_queryset.filter(Q(deployment__backend_type=backend_type))
         else:
             return parent_queryset
 
@@ -41,7 +41,7 @@
         parent_queryset = parent.get_queryset() if hasattr(parent, "get_queryset") else parent.get_query_set()
 
         if backend_type:
-            return parent_queryset.filter(Q(backend_type=backend_type)|Q(backend_type=None))
+            return parent_queryset.filter(Q(backend_type=backend_type))
         else:
             return parent_queryset
 
@@ -61,7 +61,7 @@
         parent_queryset = parent.get_queryset() if hasattr(parent, "get_queryset") else parent.get_query_set()
 
         if backend_type:
-            return parent_queryset.filter(Q(deployment__backend_type=backend_type)|Q(backend_type=None))
+            return parent_queryset.filter(Q(deployment__backend_type=backend_type))
         else:
             return parent_queryset
 
@@ -82,7 +82,7 @@
         parent_queryset = parent.get_queryset() if hasattr(parent, "get_queryset") else parent.get_query_set()
 
         if backend_type:
-            return parent_queryset.filter(Q(backend_type=backend_type)|Q(backend_type=None))
+            return parent_queryset.filter(Q(backend_type=backend_type))
         else:
             return parent_queryset