fix feature for removing commands

from a bug introduced in the 'fix parameter inheritance' change

Change-Id: I757c354130077d8838aac864b21b4f81caa9bccf
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/27096
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

test/test_modules.py

@@ -346,3 +346,16 @@ def test_command_config():
         'argument': {'type': 'bool'},
         'result': {'type': 'bool'},
     }
+
+
+def test_command_none():
+    srv = ServerStub({})
+
+    class Mod(Drivable):
+        pass
+
+    class Mod2(Drivable):
+        stop = None
+
+    assert 'stop' in Mod('o', logger, {'description': ''}, srv).accessibles
+    assert 'stop' not in Mod2('o', logger, {'description': ''}, srv).accessibles