Error in utils/segment/general masks2segments() (#9724)

When running segmentation predict on gpu, the conversion from tensor to numpy fails. Calling `.cpu()` solves this problem. 

Signed-off-by: Paul Guerrie <97041392+paulguerrie@users.noreply.github.com>

Signed-off-by: Paul Guerrie <97041392+paulguerrie@users.noreply.github.com>

utils/segment/general.py

@@ -124,7 +124,7 @@ def masks_iou(mask1, mask2, eps=1e-7):
 def masks2segments(masks, strategy='largest'):
     # Convert masks(n,160,160) into segments(n,xy)
     segments = []
-    for x in masks.int().numpy().astype('uint8'):
+    for x in masks.int().cpu().numpy().astype('uint8'):
         c = cv2.findContours(x, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)[0]
         if strategy == 'concat':  # concatenate all segments
             c = np.concatenate([x.reshape(-1, 2) for x in c])