My story has magic, and some of that magic involves manipulating pocket dimensions, hammerspace, whatever you'd like to call it. Whether it be a portal to a closet you can access with a thought, or the ability to make objects disappear and make them re-appear later, or a sleeping bag that when crawled inside leads to an entire house, a decent amount of powers, abilities and enchantments involve conjuring extra space out of nothing, in which to store things in some alternate dimension.
But this raises a rather awkward predicament I'm trying to work out how to avoid, revolving around the fact that when the person or thing a pocket dimension is tied to is destroyed, the pocket dimension associated with it is supposed to take everything from the real world that had been held inside of it and push it back out into the real world, and then disappear (anything that had been created by the magic as part of the pocket dimension, like the house in the sleeping bag example, would just vanish). This works just fine in most scenarios, but what would happen if there's no room?
Suppose a man using a pocket dimension power gets locked in a steel box that then gets encased in cement, causing him to suffocate and die. The man's pocket dimension then tries to "decompress", but the space it's emptying out into is completely airtight and won't let any more matter inside of it easily. As I see it, this can have two outcomes, both of them very, very bad for worldbuilding:
1: The pocket dimension gives up, and the matter kept inside of it is deleted and lost forever. This essentially means that anyone with one of these powers (powers which are reasonably common and can be tied to destructible objects rather than people) has the ability to completely and permanently delete matter from existence, which seems like something I really shouldn't make that easy.
2: The pocket dimension keeps pushing harder and harder, as hard as it needs to in order to get the "blockage" out of the way and dump everything inside of it out into the real world. This would introduce the concept of a hammerspace pressure bomb, which, while really, really cool, would also mean I'd never be able to do things as large as the "sleeping bag with a house inside of it" idea because the kind of explosion you could make by decompressing that kind of hammerspace would probably wind up being way more destructive force than I want to give to such commonplace magical abilities and objects.
I need an alternative method of emptying out the contents of these pocket dimensions. A method that would safely put everything inside them back into the real world within the reasonable vicinity of the source and within a maximum timeframe of about five minutes. A method that wouldn't, when met with resistance, give up and destroy the matter inside of it or apply blockage-destroying pressure.