Using backslashes inside a custom helper break compile template process.

[HugoMario]

I have a template to document PHP classes

I also created a concat helper in order to write: Package\ClassName in PHP. The custom helper used for this is:

{{concat invokerPackage '\\' classname}}{{#description}}

I've been working with this using handlerbars 4.1.2 version with no problem, recently i updated to 4.2.1 and i got an error related to compile template process when this helper is used with backslashes.

Caused by: com.github.jknack.handlebars.HandlebarsException: /handlebars/php/api_doc.mustache:24:24: found: '/vendor/autoload.php'', expected: '}}'
require_once(__DIR__ . '/vendor/autoload.php');
at com.github.jknack.handlebars.internal.HbsErrorReporter.syntaxError(HbsErrorReporter.java:93)
	at com.github.jknack.handlebars.internal.antlr.ProxyErrorListener.syntaxError(ProxyErrorListener.java:41)
	at com.github.jknack.handlebars.internal.antlr.Parser.notifyErrorListeners(Parser.java:544)
	at com.github.jknack.handlebars.internal.HbsErrorStrategy.reportInputMismatch(HbsErrorStrategy.java:186)
	at com.github.jknack.handlebars.internal.antlr.DefaultErrorStrategy.reportError(DefaultErrorStrategy.java:139)
	at com.github.jknack.handlebars.internal.HbsParser.var(HbsParser.java:1293)
	at com.github.jknack.handlebars.internal.HbsParser.statement(HbsParser.java:333)
	at com.github.jknack.handlebars.internal.HbsParser.body(HbsParser.java:231)
	at com.github.jknack.handlebars.internal.HbsParser.template(HbsParser.java:174)
	at com.github.jknack.handlebars.internal.HbsParserFactory$1.parse(HbsParserFactory.java:86)
	at com.github.jknack.handlebars.cache.NullTemplateCache.get(NullTemplateCache.java:54)
	at com.github.jknack.handlebars.Handlebars.compile(Handlebars.java:513)
	at com.github.jknack.handlebars.Handlebars.compile(Handlebars.java:438)
	at com.github.jknack.handlebars.Handlebars.compile(Handlebars.java:419)