json-parser: count defects in error msgs starting with 1

... to be consistent with cshtml's numbering of defects

Author: kdudka

json-parser.cc

@@ -49,7 +49,7 @@ struct JsonParser::Private {
         silent(silent_),
         jsonValid(false),
         hasError(false),
-        defNumber(-1)
+        defNumber(0)
     {
     }