fix(js): don't panic when escaping a string

[Conaclos]

Summary

Fix #4181

Test Plan

I added some tests to avoid any regression.

[github-actions]

Parser conformance results on

js/262

Test result	main count	This PR count	Difference
Total	48544	48544	0
Passed	47353	47353	0
Failed	1191	1191	0
Panics	0	0	0
Coverage	97.55%	97.55%	0.00%

jsx/babel

Test result	main count	This PR count	Difference
Total	40	40	0
Passed	37	37	0
Failed	3	3	0
Panics	0	0	0
Coverage	92.50%	92.50%	0.00%

symbols/microsoft

Test result	main count	This PR count	Difference
Total	6576	6576	0
Passed	2204	2204	0
Failed	4372	4372	0
Panics	0	0	0
Coverage	33.52%	33.52%	0.00%

ts/babel

Test result	main count	This PR count	Difference
Total	680	680	0
Passed	608	608	0
Failed	72	72	0
Panics	0	0	0
Coverage	89.41%	89.41%	0.00%

ts/microsoft

Test result	main count	This PR count	Difference
Total	18473	18473	0
Passed	14146	14146	0
Failed	4327	4327	0
Panics	0	0	0
Coverage	76.58%	76.58%	0.00%