Avoid inplace modifying`imgs` in `LoadStreams` (#5850)

When OpenCV retrieving image fail, original code would modify source images **inplace**, which may result in plotting bounding boxes on a black image. That is, before inference, source image `im0s[i]` is OK, but after inference before `Process predictions`, `im0s[i]` may have been changed.

Avoid inplace modifying`imgs` in `LoadStreams` (#5850)
e8f8f2b9 · Yu Zhang · GitHub · bc484579 · e8f8f2b9
--- a/utils/datasets.py
+++ b/utils/datasets.py
@@ -337,7 +337,7 @@ class LoadStreams:
                    self.imgs[i] = im
                else:
                    LOGGER.warning('WARNING: Video stream unresponsive, please check your IP camera connection.')
-                    self.imgs[i] *= 0
+                    self.imgs[i] = np.zeros_like(self.imgs[i])
                    cap.open(stream)  # re-open stream if signal was lost
            time.sleep(1 / self.fps[i])  # wait time