Fix the logic for PATH guess on Windows

Summary: Pull Request resolved: pytorch#10372

Differential Revision: D9240207

Pulled By: soumith

fbshipit-source-id: 0933f6fde19536c7da7d45044efbdcfe8ea40e1f

Author: peterjc123

torch/utils/cpp_extension.py

@@ -23,8 +23,12 @@ def _find_cuda_home():
     if cuda_home is None:
         # Guess #2
         if sys.platform == 'win32':
-            cuda_home = glob.glob(
+            cuda_homes = glob.glob(
                 'C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v*.*')
+            if len(cuda_homes) == 0:
+                cuda_home = ''
+            else:
+                cuda_home = cuda_homes[0]
         else:
             cuda_home = '/usr/local/cuda'
         if not os.path.exists(cuda_home):