Fix issues found by AddressSanitizer

Fix memcpy overlap in TIFF reader.
Fix memory leaks of SpotRows in control spot panel.
Fix memory leaks of SpotRows in locallab.
Fix memory leak of Glib::ThreadPool in file browser entry.
Fix memory leak of Glib::ThreadPool in thumbnail image updater.

rtgui/previewloader.cc

@@ -17,6 +17,7 @@
  *  along with RawTherapee.  If not, see <https://www.gnu.org/licenses/>.
  */
 
+#include <memory>
 #include <set>
 #include "cachemanager.h"
 #include "filebrowserentry.h"
@@ -81,10 +82,10 @@ public:
         int threadCount = 2;
 #endif
 
-        threadPool_ = new Glib::ThreadPool(threadCount, 0);
+        threadPool_.reset(new Glib::ThreadPool(threadCount, 0));
     }
 
-    Glib::ThreadPool* threadPool_;
+    std::unique_ptr<Glib::ThreadPool> threadPool_;
     MyMutex mutex_;
     JobSet jobs_;
     gint nConcurrentThreads;