sock_util: Allow URLs without path as valid
sock_util: Allow URLs without path as valid

URLs without a path were treated as invalid, while according to the URL
specification they are valid

Also fixes a missing null terminator in the returned path

A-Paul/RIOT,yogo1212/RIOT,rfuentess/RIOT,authmillenon/RIOT,OlegHahm/RIOT,yogo1212/RIOT,jasonatran/RIOT,toonst/RIOT,jasonatran/RIOT,avmelnikoff/RIOT,kYc0o/RIOT,miri64/RIOT,avmelnikoff/RIOT,miri64/RIOT,lazytech-org/RIOT,lazytech-org/RIOT,josephnoir/RIOT,x3ro/RIOT,ant9000/RIOT,A-Paul/RIOT,biboc/RIOT,kbumsik/RIOT,x3ro/RIOT,BytesGalore/RIOT,mfrey/RIOT,kaspar030/RIOT,jasonatran/RIOT,gebart/RIOT,avmelnikoff/RIOT,mfrey/RIOT,rfuentess/RIOT,toonst/RIOT,josephnoir/RIOT,kYc0o/RIOT,yogo1212/RIOT,rfuentess/RIOT,OTAkeys/RIOT,avmelnikoff/RIOT,authmillenon/RIOT,jasonatran/RIOT,mfrey/RIOT,avmelnikoff/RIOT,mtausig/RIOT,miri64/RIOT,kaspar030/RIOT,A-Paul/RIOT,OlegHahm/RIOT,x3ro/RIOT,kbumsik/RIOT,smlng/RIOT,OTAkeys/RIOT,aeneby/RIOT,authmillenon/RIOT,yogo1212/RIOT,yogo1212/RIOT,aeneby/RIOT,lazytech-org/RIOT,gebart/RIOT,toonst/RIOT,miri64/RIOT,authmillenon/RIOT,basilfx/RIOT,gebart/RIOT,BytesGalore/RIOT,mfrey/RIOT,toonst/RIOT,biboc/RIOT,josephnoir/RIOT,authmillenon/RIOT,x3ro/RIOT,basilfx/RIOT,lazytech-org/RIOT,kYc0o/RIOT,rfuentess/RIOT,ant9000/RIOT,josephnoir/RIOT,BytesGalore/RIOT,smlng/RIOT,mtausig/RIOT,mtausig/RIOT,BytesGalore/RIOT,cladmi/RIOT,gebart/RIOT,basilfx/RIOT,authmillenon/RIOT,kaspar030/RIOT,mtausig/RIOT,miri64/RIOT,RIOT-OS/RIOT,lazytech-org/RIOT,OlegHahm/RIOT,kYc0o/RIOT,aeneby/RIOT,gebart/RIOT,ant9000/RIOT,rfuentess/RIOT,mfrey/RIOT,basilfx/RIOT,kbumsik/RIOT,kaspar030/RIOT,OTAkeys/RIOT,josephnoir/RIOT,OlegHahm/RIOT,cladmi/RIOT,RIOT-OS/RIOT,biboc/RIOT,kaspar030/RIOT,biboc/RIOT,cladmi/RIOT,aeneby/RIOT,ant9000/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,cladmi/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,ant9000/RIOT,aeneby/RIOT,RIOT-OS/RIOT,smlng/RIOT,basilfx/RIOT,kbumsik/RIOT,OTAkeys/RIOT,toonst/RIOT,smlng/RIOT,kbumsik/RIOT,smlng/RIOT,cladmi/RIOT,A-Paul/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,biboc/RIOT,mtausig/RIOT,BytesGalore/RIOT,jasonatran/RIOT,A-Paul/RIOT,x3ro/RIOT