--Issue Summary--

Pencil2D crashes when attempting to modify a non-existing first (key)frame.

--Actual Results--

Pencil2D crashes.

--Expected Results--

Whatever is action is performed should be ignored.

--Video or Image Reference--

Attempting to use a tool on the first frame like so will cause the program to crash

--Steps to reproduce--

1. Create a new project. (This happens in existing projects too.)
2. Move the first frame of either the Bitmap layer or Vector layer to another position. (The Camera layer doesn't seem to have this problem).
3. Use a tool on the canvas. (Pencil, selection, etc.)

--System Information--

• Pencil2D Version:

Version: 0.6.1.1

• Operating System:

Operating System: Windows 10 (10.0)
CPU Architecture: x86_64

• RAM Size:

8GB

• Graphics Tablet:

WACOM Intuos CTL-490