Skip print titles and print areas when index can't be found

Print titles and areas are stored in the global DefineNames area. Matching these to worksheets can be tricky as the indexing used matches the actual position in the list of worksheets and chartsheets and "other" child objects. Other child objects generally refers to things like VBA forms that openpyxl doesn't know how to handle. As a result we can't correct the index, but we can drop the titles and areas as these are non-critical and supply a warning.

bug1825.xlsm, provided by Stephen Hill