Make ternary handling more robust

This should help with errant detection in files that use Flow. It also
makes things safer so when typing out a ternary expression, you don't
get weird flickering of major syntax region changes.

Author: amadeus

syntax/javascript.vim

@@ -137,7 +137,7 @@ syntax region  jsFuncBlock   contained matchgroup=jsFuncBraces        start=/{/
 syntax region  jsBlock       contained matchgroup=jsBraces            start=/{/  end=/}/  contains=@jsAll extend fold
 syntax region  jsSwitchBlock contained matchgroup=jsBraces            start=/{/  end=/}/  contains=@jsAll,jsLabel extend fold
 syntax region  jsObject                matchgroup=jsObjectBraces      start=/{/  end=/}/  contains=jsObjectKey,jsObjectKeyString,jsObjectKeyComputed,jsObjectSeparator,jsObjectFuncName,jsObjectGetSet,jsGenerator,jsComment,jsSpreadOperator extend fold
-syntax region  jsTernaryIf             matchgroup=jsTernaryIfOperator start=/?/  end=/:/  contains=@jsExpression
+syntax region  jsTernaryIf             matchgroup=jsTernaryIfOperator start=/?/  end=/\%(:\|[\}]\@=\)/  contains=@jsExpression
 
 syntax match   jsGenerator            contained /\*/ skipwhite skipempty nextgroup=jsFuncName,jsFuncArgs
 syntax match   jsFuncName             contained /\<[a-zA-Z_$][0-9a-zA-Z_$]*\>/ skipwhite skipempty nextgroup=jsFuncArgs