There is luk elision of āp (the feminine termination) and sup (the case-affixes) after an avyaya or indeclinable.,
Thus, तत्र शालायाम् 'in that hall'. Here the Indeclinable तत्र 'there,' does not take the feminine termination, although it is equivalent to तस्याम् 'in that.' So also कृत्वा 'having done' हित्वा &c. Here the case affix is elided.,