quant: fix conv transpose with qconfig == None (#52844)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52844
Fixes a crash in qconfig checking which happened if a model had conv transpose
with qconfig set to None.
Test Plan:
```
python test/test_quantization.py TestPostTrainingStatic.test_convtranspose_per_channel_qconfig_none
```
Imported from OSS
Reviewed By: raghuramank100
Differential Revision: D26666043
fbshipit-source-id: e1b62840b4e3c67acbb4dbdcd32514b374efce1e
