fix: ImHex crashing on exit

Fixes #698

main/source/init/tasks.cpp

@@ -4,6 +4,7 @@
 #include <imgui_freetype.h>
 
 #include <hex/api/content_registry.hpp>
+#include <hex/api/project_file_manager.hpp>
 #include <hex/ui/view.hpp>
 #include <hex/helpers/net.hpp>
 #include <hex/helpers/fs.hpp>
@@ -229,6 +230,9 @@ namespace hex::init {
             visualizers.clear();
         }
 
+        ProjectFile::getHandlers().clear();
+        ProjectFile::getProviderHandlers().clear();
+
         return true;
     }