Fix minor issues in arena.c
Fix minor issues in arena.c

kallanreed/yara,cblichmann/yara,foreni-packages/yara,wxsBSD/yara,digideskio/yara,foreni-packages/yara,pombredanne/yara,mgoffin/yara,VirusTotal/yara,frbapolkosnik/yara,cblichmann/yara,pombredanne/yara,Security513/yara,rednaga/yara,0x0mar/yara,beikezcs/yara,wxsBSD/yara,binsrc/yara,tdr130/yara,wxsBSD/yara,kallanreed/yara,msuvajac/yara,msuvajac/yara,rednaga/yara,tdr130/yara,beikezcs/yara,VirusTotal/yara,rayyang2000/yara,frbapolkosnik/yara,foreni-packages/yara,frbapolkosnik/yara,beikezcs/yara,cblichmann/yara,pombredanne/yara,MeteorAdminz/yara,jshufelt/yara,wxsBSD/yara,pombredanne/yara,rednaga/yara,Security513/yara,rayyang2000/yara,neatsun/yara,plusvic/yara,hillu/yara,digideskio/yara,tdr130/yara,0x0mar/yara,mgoffin/yara,mgoffin/yara,pombredanne/yara,jpypi/yara,0x0mar/yara,hillu/yara,MeteorAdminz/yara,digideskio/yara,msuvajac/yara,kallanreed/yara,VirusTotal/yara,neatsun/yara,bmagistro/yara,binsrc/yara,jshufelt/yara,cblichmann/yara,plusvic/yara,jshufelt/yara,smaudet/yara,jshufelt/yara,tanium/yara,plusvic/yara,digideskio/yara,jpypi/yara,MeteorAdminz/yara,Security513/yara,smaudet/yara,bmagistro/yara,hillu/yara,VirusTotal/yara,hillu/yara,hillu/yara,cblichmann/yara,rayyang2000/yara,smaudet/yara,plusvic/yara,VirusTotal/yara,binsrc/yara,0x0mar/yara,smaudet/yara,neatsun/yara,bmagistro/yara,plusvic/yara,frbapolkosnik/yara,tanium/yara,wxsBSD/yara,binsrc/yara,jpypi/yara,mgoffin/yara,tanium/yara