Fix memory leak reading v5 structure with no fields
Fix memory leak reading v5 structure with no fields

tbeu/matio,NJannasch/matio,martinichka/matio-coder,MaartenBent/matio,CBL-ORION/matio,martinichka/matio-coder,CBL-ORION/matio-sf-mirror,MaartenBent/matio,telehan/libmatio,CBL-ORION/matio,tbeu/matio,tbeu/matio,MaartenBent/matio,NJannasch/matio,telehan/libmatio,CBL-ORION/matio-sf-mirror,MaartenBent/matio,tbeu/matio,martinichka/matio-coder