PRIVATE: Fix drug bag inventory item - #7031

If an item is already in inventory, then calling Inventory() with a mask should do nothing. This fixes the drug bag in the doctor's office. It has been reappearing in ScummVM even after the player takes it.

This may be the only affected inventory item. Usually, the game scripts test an item's flag before calling Inventory() or loading the mask that leads to Inventory().

Note that there is another unrelated problem with this inventory item; Marlowe's "I took it" sound effect doesn't play in ScummVM. It is immediately interrupted by a SoundEffect() call in the next setting.

setting kDLHollowBook
{
	...
	if (kState16OrrinDead)
	{
		Bitmap("dl\search_s\dlbkocu4.bmp");
		Inventory("dl\search_s\dlbkmk9.bmp", kInventoryMarijuanaBag, kPickedUpMarijuanaBag, kDLBookcase, "inface\diary\invlist\dryinv16.bmp", "", 1, 2, "");
	}
	...
}

setting kDLBookcase
{
	if (kDrawerOpen)
	{
		SetFlag(kDrawerOpen, FALSE);
		SoundEffect("dl\audio\dlsfx002.wav");	// Slider closing
	}
	...
}