Small fix for invalid ternary detection

This was done mostly to help with crazy flow annotations since the
ternary region would cause cascading syntax breakage.  Also, a statement
like `?:` is a syntax error.

I considered adding 0 or more whitespace check as well, but I found in
practice this actually becomes annoying if you you are someone who sets
up ternary boundaries first and then fills them in after, since it won't
detect the ternary right away.

Author: amadeus

syntax/javascript.vim

@@ -155,7 +155,7 @@ syntax region  jsBlock                        matchgroup=jsBraces              s
 syntax region  jsModuleGroup        contained matchgroup=jsModuleBraces        start=/{/ end=/}/   contains=jsModuleKeyword,jsModuleComma,jsModuleAs,jsComment,jsFlowTypeKeyword skipwhite skipempty nextgroup=jsFrom fold
 syntax region  jsSpreadExpression   contained matchgroup=jsSpreadOperator      start=/\.\.\./ end=/[,}\]]\@=/ contains=@jsExpression
 syntax region  jsRestExpression     contained matchgroup=jsRestOperator        start=/\.\.\./ end=/[,)]\@=/
-syntax region  jsTernaryIf                    matchgroup=jsTernaryIfOperator   start=/?/  end=/\%(:\|}\@=\)/  contains=@jsExpression extend skipwhite skipempty nextgroup=@jsExpression
+syntax region  jsTernaryIf                    matchgroup=jsTernaryIfOperator   start=/?:\@!/  end=/\%(:\|}\@=\)/  contains=@jsExpression extend skipwhite skipempty nextgroup=@jsExpression
 syntax match   jsOperator       /?\.\ze\_D/
 
 syntax match   jsGenerator            contained /\*/ skipwhite skipempty nextgroup=jsFuncName,jsFuncArgs,jsFlowFunctionGroup