JSON: Fix parsing of a number from the end of the buffer

Avoid reading one octet past the end of the buffer when parsing a number
that is at the very end of the buffer.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/utils/json.c

@@ -165,6 +165,8 @@ static int json_parse_number(const char **json_pos, const char *end,
 			break;
 		}
 	}
+	if (pos == end)
+		pos--;
 	if (pos < *json_pos)
 		return -1;
 	len = pos - *json_pos + 1;