header_guards.py fails if file is too short

[KoBeWi]

Tested versions

4.4 1bffd6c

System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 31.0.15.4633) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

Issue description

I created a new file, applied copyright_headers.py and tried header_guards.py, but it failed with

IndexError: list index out of range
Traceback (most recent call last):
  File "C:\godot_source\misc\scripts\header_guards.py", line 74, in <module>
    lines[HEADER_CHECK_OFFSET] == HEADER_CHECK

The script expects guards at specific line, but if file is too short, it goes out of bounds.

Steps to reproduce

1. Create new .h file in Godot source directory
2. Run python misc/scripts/header_guards.py path/to/that/file.h

Minimal reproduction project (MRP)

https://github.com/godotengine/godot/archive/refs/heads/master.zip