get_key() silently drops first path segment when key_path has no leading backslash

[mkorman90]

RegistryHive.get_key() splits on \ and takes [1:], assuming a leading backslash. Without it, the first real segment (e.g., ControlSet001) is silently dropped:

# FAILS — "ControlSet001" dropped, looks for "Control" under root
reg.get_key("ControlSet001\\Control\\ComputerName\\ComputerName")

# WORKS — leading backslash makes [1:] discard empty string
reg.get_key("\\ControlSet001\\Control\\ComputerName\\ComputerName")