Yes, at least you should consider it to.
Rules (not exhaustive at all) that I was taught to obey at all times (and afaik that's generally a mantra of the "weapons-community" around here):
- Every weapon is to be considered charged at all times.
- Never point your weapon at anything unless you want to shoot at it.
For these rules to make any sense, shit (e.g. unplanned discharge) must be able to happen, which is also postulated by Murphy. Discharging while resting qualifies as (dangerous) shit, so you should consider it possible to happen.
That's also the reason why weapons are always deponated facing in a direction, where shooting would do least damage, why your rifle should always point to the ground while carrying, ...
This answer is based on the limited weapons experience of +-21 weeks of obligatory military service and heavily biased towards erring on the safe side, and in addition only targets the title question, not so much the body, but I believe it still has some merit. For a detailed answer, refer e.g. to the one by Charlie. Lets see if it survives the QA process :)