fix(demo): ignore zero bytes for bl ip

Signed-off-by: sakumisu <1203593632@qq.com>

demo/video_audiov1_hid_template.c

@@ -448,6 +448,10 @@ void usbd_video_close(uint8_t busid, uint8_t intf)
 
 void usbd_video_iso_callback(uint8_t busid, uint8_t ep, uint32_t nbytes)
 {
+    if (nbytes == 0) {
+        return;
+    }
+
     if (usbd_video_stream_split_transfer(busid, ep)) {
         /* one frame has done */
         video_iso_tx_busy = false;

demo/video_static_h264_template.c

@@ -252,6 +252,10 @@ void usbd_video_close(uint8_t busid, uint8_t intf)
 
 void usbd_video_iso_callback(uint8_t busid, uint8_t ep, uint32_t nbytes)
 {
+    if (nbytes == 0) {
+        return;
+    }
+
     if (usbd_video_stream_split_transfer(busid, ep)) {
         /* one frame has done */
         iso_tx_busy = false;

demo/video_static_mjpeg_template.c

@@ -252,6 +252,10 @@ void usbd_video_close(uint8_t busid, uint8_t intf)
 
 void usbd_video_iso_callback(uint8_t busid, uint8_t ep, uint32_t nbytes)
 {
+    if (nbytes == 0) {
+        return;
+    }
+
     if (usbd_video_stream_split_transfer(busid, ep)) {
         /* one frame has done */
         iso_tx_busy = false;

demo/video_static_yuyv_template.c

@@ -256,6 +256,10 @@ void usbd_video_close(uint8_t busid, uint8_t intf)
 
 void usbd_video_iso_callback(uint8_t busid, uint8_t ep, uint32_t nbytes)
 {
+    if (nbytes == 0) {
+        return;
+    }
+
     if (usbd_video_stream_split_transfer(busid, ep)) {
         /* one frame has done */
         iso_tx_busy = false;