Fixed a little bug that make Spacebar unable to be invoked as sms handler

Hi, i have a Pinephone with PostmarketOS and Plasma Mobile. I have noticed that plasma-phonebook is not able to open spacebar when clicking on Write message on "phone number". After a bit of digging on the problem seems spacebar is not recognized by the system as a valid sms handler because of the missing mimetype. Also the klauncher said: Unknown protocol 'sms' error is throwed if "%u" is missing on the exec line. Seems like the missing parameters passed with "%u" makes some problems to klauncher, but i'm not 100% sure. I have tried to mimic the plasmaphonedialer desktop file that make it correctly invocable by plasma-phonebook and seems to work.

To be noticed: even with this little fix, Spacebar will only open on the main page; for example opening Spacebar from a contact plasma-phonebook will not open to the recipient page. Even running from the terminal spacebar sms:"phone number" will only open Spacebar to the main page (i have tried some combination of phone numbers without success).

Thanks for listening, have a good day