--save-txt extension fix

detect.py

@@ -124,7 +124,7 @@ def detect(save_img=False):
                 for *xyxy, conf, cls in det:
                     if save_txt:  # Write to file
                         xywh = (xyxy2xywh(torch.tensor(xyxy).view(1, 4)) / gn).view(-1).tolist()  # normalized xywh
-                        with open(save_path + '.txt', 'a') as file:
+                        with open(save_path[:save_path.rfind('.')] + '.txt', 'a') as file:
                             file.write(('%g ' * 5 + '\n') % (cls, *xywh))  # label format
 
                     if save_img or view_img:  # Add bbox to image