Merge pull request #7020 from radarhere/no_libtiff

Author: hugovk

src/PIL/TiffImagePlugin.py

@@ -1807,7 +1807,7 @@ def _save(im, fp, filename):
             # Custom items are supported for int, float, unicode, string and byte
             # values. Other types and tuples require a tagtype.
             if tag not in TiffTags.LIBTIFF_CORE:
-                if not Image.core.libtiff_support_custom_tags:
+                if not getattr(Image.core, "libtiff_support_custom_tags", False):
                     continue
 
                 if tag in ifd.tagtype: