Syntax highlighting broken if a variable is used with bash source

[feliksik]

The following breaks syntax highlighting:

= bug

== Header 1

:x: foo

.check version on Windows
[source, subs="attributes"]
----
{x}
----

== Highlighting is still ok
// syntax highlighting is still fine

.check version on Windows
[source, bash, subs="attributes"]
----
{x}
----

== Syntax highlighting is now broken

It's caused by the {x} string in combination with the 'bash' argument to the source block. 

It looks like this:

If I don't use 'bash' but 'python' as language, it does work as expected...