Remove unnnecessary NUL termination of yytext (as it may contain NULs)

src/json.hpp

@@ -1828,9 +1828,6 @@ class lexer
                 // closing quote
                 case '\"':
                 {
-                    // terminate yytext
-                    add('\0');
-                    --yylen;
                     return token_type::value_string;
                 }
 
@@ -2576,10 +2573,6 @@ scan_number_done:
         // we are done scanning a number)
         unget();
 
-        // terminate token
-        add('\0');
-        --yylen;
-
         char* endptr = nullptr;
         errno = 0;