fix error when there are no related events/signatures, or simply signatures
fix error when there are no related events/signatures, or simply
signatures

elhoim/MISP,Maijin/MISP,x86Labs/MISP,crruthe/MISP,jiekechoo/MISP,SteveClement/MISP,TheDr1ver/MISP,aaronkaplan/MISP,Maijin/MISP,FIRSTdotorg/MISP,SteveClement/MISP,devnull-/MISP,FloatingGhost/MISP,Maijin/MISP,aaronkaplan/MISP,TheDr1ver/MISP,jiekechoo/MISP,FIRSTdotorg/MISP,0x0mar/MISP,cristianbell/MISP,devnull-/MISP,regit/MISP,triplekill/MISP,regit/MISP,FloatingGhost/MISP,Rafiot/MISP,FIRSTdotorg/MISP,Rafiot/MISP,MISP/MISP,regit/MISP,x86Labs/MISP,regit/MISP,pombredanne/MISP,RichieB2B/MISP,jiekechoo/MISP,MISP/MISP,crruthe/MISP,triplekill/MISP,TheDr1ver/MISP,devnull-/MISP,SteveClement/MISP,triplekill/MISP,0x0mar/MISP,x86Labs/MISP,0x0mar/MISP,cristianbell/MISP,x86Labs/MISP,Maijin/MISP,Rafiot/MISP,MISP/MISP,devnull-/MISP,FloatingGhost/MISP,MISP/MISP,cristianbell/MISP,SteveClement/MISP,0x0mar/MISP,FIRSTdotorg/MISP,triplekill/MISP,FloatingGhost/MISP,MISP/MISP,aaronkaplan/MISP,crruthe/MISP,RichieB2B/MISP,pombredanne/MISP,jiekechoo/MISP,cristianbell/MISP,crruthe/MISP,elhoim/MISP,RichieB2B/MISP,RichieB2B/MISP,aaronkaplan/MISP,elhoim/MISP,pombredanne/MISP,elhoim/MISP,Rafiot/MISP,pombredanne/MISP,SteveClement/MISP,TheDr1ver/MISP