Cast nn.Upsample.scale_factor to a float (#17732)

Summary:
Fixes #17106
Pull Request resolved: #17732

Differential Revision: D14388192

Pulled By: driazati

fbshipit-source-id: d9c9e87a7c6db63c1de3ddebbb8dcf619f0dc34d

torch/nn/modules/upsampling.py

@@ -126,7 +126,7 @@ def __init__(self, size=None, scale_factor=None, mode='nearest', align_corners=N
         super(Upsample, self).__init__()
         self.name = type(self).__name__
         self.size = size
-        self.scale_factor = scale_factor
+        self.scale_factor = float(scale_factor) if scale_factor else None
         self.mode = mode
         self.align_corners = align_corners