Fix a segfault under low memory conditions
Fix a segfault under low memory conditions

yr_atoms_extract_from_re and  yr_atoms_extract_from_re functions were returning a non-null list of atoms even if failing, a segfault occurred while the calling function tried to destroy the returned list which was already destroyed.

mgoffin/yara,VirusTotal/yara,neatsun/yara,pombredanne/yara,jshufelt/yara,hillu/yara,tdr130/yara,tdr130/yara,rayyang2000/yara,neatsun/yara,jpypi/yara,plusvic/yara,jshufelt/yara,plusvic/yara,pombredanne/yara,MeteorAdminz/yara,neatsun/yara,smaudet/yara,smaudet/yara,MeteorAdminz/yara,pombredanne/yara,msuvajac/yara,rednaga/yara,cblichmann/yara,bmagistro/yara,hillu/yara,kallanreed/yara,wxsBSD/yara,rayyang2000/yara,cblichmann/yara,tdr130/yara,Security513/yara,beikezcs/yara,pombredanne/yara,rednaga/yara,cblichmann/yara,jshufelt/yara,bmagistro/yara,msuvajac/yara,jpypi/yara,frbapolkosnik/yara,wxsBSD/yara,VirusTotal/yara,kallanreed/yara,hillu/yara,beikezcs/yara,mgoffin/yara,rednaga/yara,plusvic/yara,plusvic/yara,MeteorAdminz/yara,foreni-packages/yara,hillu/yara,msuvajac/yara,foreni-packages/yara,frbapolkosnik/yara,VirusTotal/yara,rayyang2000/yara,wxsBSD/yara,VirusTotal/yara,frbapolkosnik/yara,Security513/yara,wxsBSD/yara,tanium/yara,bmagistro/yara,kallanreed/yara,smaudet/yara,jshufelt/yara,pombredanne/yara,wxsBSD/yara,smaudet/yara,cblichmann/yara,tanium/yara,cblichmann/yara,hillu/yara,beikezcs/yara,VirusTotal/yara,mgoffin/yara,jpypi/yara,mgoffin/yara,frbapolkosnik/yara,plusvic/yara,tanium/yara,Security513/yara,foreni-packages/yara