Correct not moving frame index when reading imu data

src/filewriter.cpp

@@ -254,7 +254,7 @@ void IMUFileWriter::write(uint8_t *sample, size_t size, uint8_t *imu_data) {
                     break;
             }
         }
-        //
+        imu_data_cur += frame_size;
     }
 }