Issue Summary

Whenever you move a a few frames, the canvas will show the wrong content.

Actual Results

Moving frames will result in wrong content on the canvas

Expected Results

Canvas should always show the correct content.

Video reference

Steps to reproduce

• Draw 4 or more frames concurrently
• Select all frames and move them 1-2 frames to the right
  Notice that frame 1 is gone and other frames may be swapped.

System Information

• Pencil2D Version:
• master - latest commit(bdf7365)