No not safe!
Actually rather dangerous and illegal as hell in the UK too.
... "The 'Electricity at Work Regulations 1989' in Regulations 4(1) and 4(2) lay down the requirement to ensure that an electrical installation should be designed, installed, constructed and maintained in a safe manner at all times. The basis for periodic inspection and testing is derived from Guidance Note 3 of the 'IEE Wiring Regulations BS7671:2008'. "
A guitar (certainly if used professionally) is subject to statutory Portable Appliance Testing (PAT)
Earth Bond Test
Readings should show less than 0.1+R Ohms (where R is the resistance of the lead)
Tested at a current of 1.5 times the rating of the fuse and no greater than 25A for a period of between 5 and 20 seconds ...
That bridge string "ground" is not at earth by 220k and a big storage cap. Eek!
- it failed, Oops!
1) That capacitor can store a charge between true earth and the guitar hardware, certainly enough to give you a nasty fright if a fault develops
2) if a fault develops on set and the guitar touches a live connection, then rather than dumping down the earth strap as intended (and tripping the RCD), you get to be the earth conductor and get a trip in the ambulance.