fix crash in lru_map/SalBitmap on shutdown

When we shut down, we destroy the various caches, in the process of
which SalBitmap calls back into it's owning cache, causing a SIGSEGV.

Found while loading files from tdf#83426

Change-Id: I53db1621a0fdb75a8e66582662b0e2666499192b
Reviewed-on: https://gerrit.libreoffice.org/73387
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

include/o3tl/lru_map.hxx

@@ -69,6 +69,14 @@ public:
     lru_map(size_t nMaxSize)
         : mMaxSize(nMaxSize ? nMaxSize : std::min(mLruMap.max_size(), mLruList.max_size()))
     {}
+    ~lru_map()
+    {
+        // Some code .e.g. SalBitmap likes to remove itself from a cache during it's destructor, which means we
+        // get calls into lru_map while we are in destruction, so use the swap-and-clear idiom to avoid those problems.
+        mLruMap.clear();
+        list_t aLruListTemp;
+        aLruListTemp.swap(mLruList);
+    }
 
     void insert(key_value_pair_t& rPair)
     {