Do not restrict the falsy values of bindings on pick_binding method

Signed-off-by: Ivan Kanakarakis <[email protected]>

Author: c00kiemon5ter

src/saml2/entity.py

@@ -305,7 +305,7 @@ def pick_binding(
 
         sfunc = getattr(self.metadata, service)
 
-        if bindings is None:
+        if not bindings:
             if request and request.protocol_binding:
                 bindings = [request.protocol_binding]
             else: