fix: zero-based index

[golergka]

What does this PR do?

My project uses yaml-language-server, and I got these errors in Sentry:

Error: Range#create called with invalid arguments[1682, -1, 1682, 0]
4    at Object.e.create
5  at Object.e.create
6  at Zl.getLineCharCode

Unfortunately, I wasn't able to reproduce this error, so all my work is just following the stacktrace.

What issues does this PR fix or reference?

The only place where the function getLineCharCode is used is here:

yaml-language-server/src/languageservice/utils/indentationGuesser.ts

Lines 136 to 138 in eae5206

	for (let j = 0, lenJ = currentLineLength; j < lenJ; j++) {
	const charCode = useCurrentLineText ? currentLineText.charCodeAt(j) : source.getLineCharCode(lineNumber, j);

Both surrounding code and description on charCodeAt suggest that this index should be 0-based, but the getLineCharCode is written with a 1-based index in mind, which seems like the source of this bug.

Is it tested? How?

I wasn't able to reproduce the original issue, so it's hard for me to test this fix.

[coveralls]

Coverage remained the same at 82.58% when pulling 9fe98e8 on golergka:fix/zero-based-index into eae5206 on redhat-developer:main.

[evidolob]

LGTM

[msivasubramaniaan]

LGTM