Refresh module handle if NULL when hitting GetProcAddress

* This might be a more serious problem in future...
* We only hook all loaded modules once, at init time, in Win32_IAT_EndHooks
* If a LoadLibrary call afterwards implicitly loads some modules we don't
  see them. Potentially we should rehook all loaded modules again each time
  LoadLibrary is called but then there would be a lot of redundant work
  unless we tracked module unload/loads to see if a module has been hooked
  before or not. For now assume we don't need to hook these modules and
  get away with just updating module handles