change default QUANTIZATION.MODULES to []

Summary: Might causing https://github.com/facebookresearch/d2go/issues/113.

Reviewed By: kazhang

Differential Revision: D31066641

fbshipit-source-id: 563c2cb255b1cca4a12c8adfafc7380f140efde5

d2go/modeling/quantization.py

@@ -79,7 +79,7 @@ def add_quantization_default_configs(_C):
     # used to enable metarch set_custom_qscheme (need to implement)
     # this is a limited implementation where only str is provided to change options
     _C.QUANTIZATION.CUSTOM_QSCHEME = ""
-    _C.QUANTIZATION.MODULES = None
+    _C.QUANTIZATION.MODULES = []
     # Lightning quantization callback name
     _C.QUANTIZATION.NAME = ""