Potential Null Pointer Dereference caused by `_zip_ef_new`

https://github.com/nih-at/libzip/blob/e16526dbb751dc31129b32ba667ce6aed5c42f97/lib/zip_extra_field.c#L177-L198 After scan the code of `_zip_ef_new`, we can found that it is a function to allocate the memory. However, it has the potential to fail. I have two potentail missing the return value check. ### case 1 https://github.com/nih-at/libzip/blob/e16526dbb751dc31129b32ba667ce6aed5c42f97/lib/zip_dirent.c#L971-L973 ### case 2 https://github.com/nih-at/libzip/blob/e16526dbb751dc31129b32ba667ce6aed5c42f97/lib/zip_dirent.c#L1000-L1002