fix another segfault

src/zm_local_camera.cpp

@@ -2135,12 +2135,16 @@ int LocalCamera::PostCapture()
                     return( -1 );
                 }
             }
+			if ( v4l2_data ) {
             Debug( 3, "Requeueing buffer %d", v4l2_data.bufptr->index );
             if ( vidioctl( vid_fd, VIDIOC_QBUF, v4l2_data.bufptr ) < 0 )
             {
                 Error( "Unable to requeue buffer %d: %s", v4l2_data.bufptr->index, strerror(errno) )
                 return( -1 );
             }
+			} else {
+                Error( "Unable to requeue buffer due to not v4l2_data" )
+			}
         }
 #endif // ZM_HAS_V4L2
 #if ZM_HAS_V4L1