Tracker: Remove failing ASSERT

This ASSERT causes a crash in the debug build of libtracker.so.

The crash occurs when two conditions are met:
1. There are files in the directory with icons specific to them. This
   is the case with image files, whose icons preview what the contents
   of the image are.
2. Tracker has not displayed those icons yet. This happens if the user
   has not scrolled down far enough to see the icons.

One way to meet these conditions is to configure the build system to
compile a debug build of libtracker.so. Then compile icon-o-matic.
Then run icon-o-matic with the debug build of libtracker.so
LD_PRELOAD'ed.

With that, press File->Open and navigate to
/system/documentation/BeBook/images/admonitions. While in the images
folder, do not scroll up or down to view the icons of the images in the
folder. They should remain unrendered. It should crash as soon as
Tracker enters the admonitions folder.

The crash occurs because NodeIconCache::Deleting is called without a
corresponding call to NodeIconCache::AddItem. Tracker calls
NodeIconCache::AddItem whenever it renders an icon to cache the result.
Tracker, however, is lazy, and only renders the icon when it comes into
view. When navigating out of the directory, Tracker has to call
Deleting for every file in the directory since it doesn't keep track of
which icons it rendered and which icons it didn't. Thus, AddItem has
been called for some of the files, but Deleting has been called for all
of them, causing the assert to fail and the program to crash.

This commit fixes the problem by not requiring a call to AddItem for
each call to Deleting.

Change-Id: I1038ce70ca345c44812becee7f3752567e5b562a
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6474
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: waddlesplash <[email protected]>

src/kits/tracker/IconCache.cpp

@@ -1743,7 +1743,6 @@ void
 NodeIconCache::Deleting(const node_ref* node)
 {
 	NodeCacheEntry* entry = FindItem(node);
-	ASSERT(entry != NULL);
 	if (entry == NULL || entry->Permanent())
 		return;