[bug] set default value for "Content-Length"
[bug] set default value for "Content-Length"

Setting default value as -1 when "Content-Length" is empty. If not, currently it will raise a ValueError
bottlepy/bottle,oz123/bottle,defnull/bottle,fkazimierczak/bottle,defnull/bottle,bottlepy/bottle,oz123/bottle,fkazimierczak/bottle