Error upon entering AV

Sometimes I get the following error when entering an AV:

Date: 2020-01-04 18:17:21
ID: 1
Error occured in: Global
Count: 1
Message: …erfaceAddOnsDugisGuideViewerZDugisGuideViewer.lua line 4470:
   attempt to call method ‘UNIT_QUEST_LOG_CHANGED’ (a nil value)
Debug:
   [C]: UNIT_QUEST_LOG_CHANGED()
   …erfaceAddOnsDugisGuideViewerZDugisGuideViewer.lua:4470: ?()
   …erfaceAddOnsDugisGuideViewerZDugisGuideViewer.lua:180:
      …erfaceAddOnsDugisGuideViewerZDugisGuideViewer.lua:163
   [C]: ?
Locals:

AddOns:
  Swatter, v8.2.6377 (SwimmingSeadragon)
  AddOnSkins, v4.39
  AdiBags, vDEV
  AdiBagsItemRackSets, vv1.5
  aPVPName1s2s, v1.31
  AtlasLootClassic, vv1.4.4
  AtlasLootClassicData, vv1.4.4
  AtlasLootClassicDungeonsAndRaids, vv1.4.4
  AtlasLootClassicMaps, vv1.0.0
  AucAdvanced, v8.2.6430 (SwimmingSeadragon)
  AucFilterBasic, v8.2.6364 (SwimmingSeadragon)
  AucScanData, v8.2.6365 (SwimmingSeadragon)
  AucStatHistogram, v8.2.6366 (SwimmingSeadragon)
  AucStatiLevel, v8.2.6370 (SwimmingSeadragon)
  AucStatPurchased, v8.2.6367 (SwimmingSeadragon)
  AucStatSimple, v8.2.6399 (SwimmingSeadragon)
  AucStatStdDev, v8.2.6369 (SwimmingSeadragon)
  AucUtilFixAH, v8.2.6371 (SwimmingSeadragon)
  BeanCounter, v8.2.6434 (SwimmingSeadragon)
  ChatThrottleLib, v23
  ClassicSpellActivations, v
  DBMCore, v1.13.28
  DBMDefaultSkin, v
  DBMStatusBarTimers, v
  Decursive, v2.7.6.6
  DejaClassicStats, v1303r001
  Details, v
  DetailsTinyThreat, v
  DugisGuideViewerZ, v1.116
  ElvUI, v1.19
  ElvUILocationPlus, v1.02
  ElvUIRaidMarkers, v5.1.3
  Enchantrix, v8.2.6428 (SwimmingSeadragon)
  EnchantrixBarker, v8.2.6469 (SwimmingSeadragon)
  FishingBuddy, v0.7.2 Beta 2
  GatherMate2, v1.45.5
  GroupCalendar, v
  honorspy, v1.7.1
  HonorTracker, vv3.2.3
  Informant, v8.2.6374 (SwimmingSeadragon)
  ItemRack, v
  LeatrixPlus, v1.13.43
  LFGMatchMaker, v1.0.3
  lsToasts, v11302.02
  Masque, v8.2.8-Classic
  MasqueElvUIesque, v1.0
  MissingTradeSkillsList, v1.13.29
  NameplateSCT, v1.5
  NeatPlates, v1.13.3.6
  NeatPlatesQuatre, v
  NeatPlatesHub, v
  NeatPlatesWidgets, v
  Questie, v5.4.1
  RealMobHealth, v2.17
  SkilletClassic, v1.09
  SSPVP, v
  Stubby, v8.2.6376 (SwimmingSeadragon)
  Talented, vv191112
  TalentedData, v
  UsedInRecipe, v1.0.3
  WhatsTraining, v1.8.7
  BlizRuntimeLib_enUS v1.13.3.11303 <none>
  (ck=712)