Scripting/Blade's Edge: Quest 10594 "Gauging the Resonant Frequency"
Closes #6214
Core/SpellMgr: Remove unneeded check for max targets
Core/Commands: Fix NULL dereference crash in .npc set link

Fix NULL dereference crash in .npc set link happening when passing a not-existent Creature guid as parameter, es. ".npc set link -1" .
Issue spotted by static analysis, added in c05ed659cbc561b6e7c0016cc7b1548886d5337a