Legally yes, as the combo gives him access.
Reality check time -
99.99% of the time there will be no issue, it will never be noticed or raised as an issue. I've had a carry license since 1983 and in only two cases did I need to display it to law enforcement - both of which were very routine and too boring to relate here. You are dealing with "what happens if...." edge cases. The approach is not to look only at what the law actually says, but how it is likely to be applied. For example, how many people have actually avoid being charged with possession of a firearm on school property by pointing out to the police that the gun was not on their person while bing possessed in on school property? The law is clear on that one, but practice is nearly universally consistent with the MA law where the handcuffs meet the wrist.
.0001% of the time something will happen. For example, if a warrant is served on your friend (perhaps a service person notices the safe, assumes you have guns, and reports it to the PD), the police are unlikely to accept "....not covered by the warrant, leased property". And as to you friend not being in possession - charges would likely be filed and, with proper preparation, he would have a good offense (are you going to reimburse him since he was doing a favor for you?). If you go that "Safe in unlicensed friend's place" you may wish to consider a printed notice on the safe "Property of ...... ; no other person has combination; consent to search valid only if granted in writing by ......." to establish clear notice rather than make it look like an ex post facto justification.
Good lawyers like Tassel, Langer and others know not only the law but how things go down in practice. Hire, pay and heed their advice.