json-lexer: Initialize 'x' and 'y'

The 'lexer' variable is passed by the caller, it can contain anything
(eg. garbage).

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

json-lexer.c

@@ -275,6 +275,7 @@ void json_lexer_init(JSONLexer *lexer, JSONLexerEmitter func)
     lexer->emit = func;
     lexer->state = IN_START;
     lexer->token = qstring_new();
+    lexer->x = lexer->y = 0;
 }
 
 static int json_lexer_feed_char(JSONLexer *lexer, char ch)