Core/Spells: Change a log message to debug level and make it more descriptive.

src/server/game/Spells/Spell.cpp

@@ -2258,7 +2258,7 @@ void Spell::SelectEffectTargets(uint32 i, uint32 cur)
         {
             if (!m_originalCaster || !m_originalCaster->GetCurrentSpell(CURRENT_CHANNELED_SPELL))
             {
-                sLog->outError("SPELL: no current channeled spell for spell ID %u", m_spellInfo->Id);
+                sLog->outDebug(LOG_FILTER_SPELLS_AURAS, "SPELL: no current channeled spell for spell ID %u - spell triggering this spell was interrupted.", m_spellInfo->Id);
                 break;
             }