typo in K-File-IO/code/practice.md

[dahuachen]

Test 3, Case 1:
The line
Buffer now contains: world\0\0\0\0\0hello\n
should be
Buffer now contains: world\0\0\0\0\0hello\0

[hmontero1205]

test might need to be redesigned.. a little confusing. there should be no null terminator? but then you cant print it