you need a conditional check, when you got a conditional (object that has the verb vs object that doesn't have the verb), example:
<function name="your_verbs_scripting_function" parameters="object_x">
if (HasScript (object_x, "your_verbs_name") {
// do your wear scripting
} else {
msg ("This action is not possible with this object.")
}
</function>
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you can save scripting redundency by using a function to hold your scripting, then you simply 'call upon' (add a script) within your Verb, Command, or whatever other Element.
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you can add Chase's Wearables Library to your game, as otherwise, if quest doesn't have it's own built in 'unwear~remove' Verb, you'd have to make your own, obviously.