Fix App memory leak

[lenemter]

The issue was in GLib.HashTable.steal_extended use. The whole point of steal* methods is to transfer ownership of the objects without calling destroy functions. But since the second argument (stolen key) was null, the ownership was never transferred and destroy function (unref if this case) was never called, which lead to memory leak.

Instead of dealing with convoluted method, just use @get and remove.

[leolost2605]

Could we use GLib.HashTable.take ()? Would make it just a little bit more readable IMO

[lenemter]

@leolost2605 GLib.HashTable.take () is basically GLib.HashTable.steal () under the hood:

public V? take (K key, out bool exists = null) {
	GLib.HashTable<K,V>? ht = null;
	void** htp = &ht;
	*htp = this.lookup (key);
	exists = this.steal (key);
	return ht;
}

GLib.HashTable.steal () "removes a key and its associated value from a GLib.HashTable without calling the key and value destroy functions", so basically the same issue as in GLib.HashTable.steal_extended

[leolost2605]

Too bad, I thought since it's a vala method take would take care of the key or just do it differently altogether but ig not :(

https://gitlab.gnome.org/GNOME/vala/-/work_items/1664