Core: Don't thow an error if lookbehing is used without anything matching.

Golmote · Golmote · commit e0cd47f8392d · 2018-03-03T20:14:23.000+01:00
diff --git a/components/prism-core.js b/components/prism-core.js
@@ -356,7 +356,7 @@ var _ = _self.Prism = {
 					}
 
 					if(lookbehind) {
-						lookbehindLength = match[1].length;
+						lookbehindLength = match[1] ? match[1].length : 0;
 					}
 
 					var from = match.index + lookbehindLength,
diff --git a/components/prism-core.min.js b/components/prism-core.min.js
diff --git a/prism.js b/prism.js
@@ -361,7 +361,7 @@ var _ = _self.Prism = {
 					}
 
 					if(lookbehind) {
-						lookbehindLength = match[1].length;
+						lookbehindLength = match[1] ? match[1].length : 0;
 					}
 
 					var from = match.index + lookbehindLength,

Original file line number	Diff line number	Diff line change
`@@ -356,7 +356,7 @@ var _ = _self.Prism = {`
`356`	`356`	`}`
`357`	`357`
`358`	`358`	`if(lookbehind) {`
`359`		`- lookbehindLength = match[1].length;`
	`359`	`+ lookbehindLength = match[1] ? match[1].length : 0;`
`360`	`360`	`}`
`361`	`361`
`362`	`362`	`var from = match.index + lookbehindLength,`
Original file line number	Diff line number	Diff line change
`@@ -361,7 +361,7 @@ var _ = _self.Prism = {`
`361`	`361`	`}`
`362`	`362`
`363`	`363`	`if(lookbehind) {`
`364`		`- lookbehindLength = match[1].length;`
	`364`	`+ lookbehindLength = match[1] ? match[1].length : 0;`
`365`	`365`	`}`
`366`	`366`
`367`	`367`	`var from = match.index + lookbehindLength,`