Invite button in shortcut bar does not work

[nmiketta]

Describe the bug Clicking the invite button in the shortcut bar in an open chat window does not invite the chat partner.

To Reproduce Steps to reproduce the behavior:

1. Whisper a player or receive a whisper from a player to open a chat window
2. Click on 'Invite to Party' in the shortcut bar
3. See error

Expected behavior The chat partner should be invited

BugSack output

1x WIM\Modules\ShortcutBar.lua:357: attempt to call field 'InviteUnit' (a nil value)
[string "@WIM\Modules\ShortcutBar.lua"]:357: in function `OnClick'
[string "@WIM\Modules\ShortcutBar.lua"]:53: in function <WIM\Modules\ShortcutBar.lua:51>

Locals:
self = WIM_ShortcutBarButton2 {
 0 = <userdata>
 index = 2
 PixelSnapDisabled = true
 SetDefaults = <function> defined @WIM\Modules\ShortcutBar.lua:56
 parentWindow = WIM3_msgFrame1 {
 }
 isEnabled = true
 Enable = <function> defined @WIM\Modules\ShortcutBar.lua:25
 icon = <unnamed> {
 }
 Disable = <function> defined @WIM\Modules\ShortcutBar.lua:30
}
win = WIM3_msgFrame1 {
 0 = <userdata>
 Hide_Normal = <function> defined =[C]:-1
 class = ""
 isNew = false
 offScreen = 0
 level = ""
 SendWho = <function> defined @WIM\Sources\WindowHandler.lua:995
 animators = <table> {
 }
 animation = <table> {
 }
 WhoCallback = <function> defined @WIM\Sources\WindowHandler.lua:983
 isWimWindow = true
 age = 435683.373000
 unreadCount = 0
 msgWaiting = false
 Hide = <function> defined @WIM\Sources\WindowHandler.lua:1224
 bn = <table> {
 }
 SafeGetTop = <function> defined @WIM\Sources\WindowHandler.lua:1272
 UpdateCharDetails = <function> defined @WIM\Sources\WindowHandler.lua:979
 AddMessage = <function> defined @WIM\Sources\WindowHandler.lua:884
 helperFrame = WIM_WindowHelperFrame {
 }
 SafeGetRight = <function> defined @WIM\Sources\WindowHandler.lua:1269
 UpdateIcon = <function> defined @WIM\Sources\WindowHandler.lua:906
 hasMoved = false
 customSize = false
 guild = ""
 SetScale_Orig = <function> defined =[C]:-1
 GetRuleSet = <function> defined @WIM\Sources\WindowHandler.lua:1100
 race = ""
 lastActivity = 435683.373000
 UpdateProps = <function> defined @WIM\Sources\WindowHandler.lua:1175
 classColor = "ffffff"
 AddEventMessage = <function> defined @WIM\Sources\WindowHandler.lua:895
 initialized = true
 SetScale = <function> defined @WIM\Sources\WindowHandler.lua:778
 fadeOut = <function> defined @WIM\Sources\WindowHandler.lua:820
 type = "whisper"
 isParent = true
 SafeGetLeft = <function> defined @WIM\Sources\WindowHandler.lua:1266
 ResetAnimation = <function> defined @WIM\Sources\WindowHandler.lua:1252
 widgets = <table> {
 }
 SafeGetBottom = <function> defined @WIM\Sources\WindowHandler.lua:1275
 online = true
 theUser = "Hkjshjkshs"
 Pop = <function> defined @WIM\Sources\WindowHandler.lua:1110
 location = ""
 AddMessageRaw = <function> defined @WIM\Sources\WindowHandler.lua:891
 fadeIn = <function> defined @WIM\Sources\WindowHandler.lua:819
 fadedIn = true
}
(*temporary) = nil
(*temporary) = "Hkjshjkshs"
(*temporary) = "attempt to call field 'InviteUnit' (a nil value)"
_G = <table> {
 1 = <no value>
 ERR_OUT_OF_CHI = "Not enough chi"
 DH_HAVOC_CORE_ABILITY_2 = "Strong melee attack that consumes Fury. If it critical strikes, some Fury is refunded."
 GetTrainerServiceTypeFilter = <function> defined =[C]:-1
 UNIT_NAMES_COMBATLOG_TOOLTIP = "Color unit names."
 SetTrainerServiceTypeFilter = <function> defined =[C]:-1
 LE_GAME_ERR_CHAT_RAID_RESTRICTED_TRIAL = 741
 SPELL_FAILED_CUSTOM_ERROR_71 = "This partygoer wants to dance with you."
 LE_GAME_ERR_PET_SPELL_TARGETS_DEAD = 400
 CompactUnitFrameProfilesGeneralOptionsFrameHealthTextDropdownButtonNormalTexture = CompactUnitFrameProfilesGeneralOptionsFrameHealthTextDropdownButtonNormalTexture {
 }
 FriendsListFrameScrollFrameButton20TravelPassButtonPushedTexture = FriendsListFrameScrollFrameButton20TravelPassButtonPushedTexture {
 }
 MultiBarLeftButton7 = MultiBarLeftButton7 {
 }
 AudioOptionsVoicePanelOutputDeviceDropdownButtonHighlightTexture = AudioOptionsVoicePanelOutputDeviceDropdownButtonHighlightTexture {
 }
 LE_GAME_ERR_INVALID_FOLLOW_PVP_COMBAT = 354
 MerchantItem4AltCurrencyFrameItem1Text = MerchantItem4AltCurrencyFrameItem1Text {
 }
 BINDING_NAME_NAMEPLATES = "Show Enemy Name Plates"
 CHAT_HEADER_SUFFIX = ": "
 EncounterDetails_SpellAurasScrollScrollChildFrame = EncounterDetails_SpellAurasScrollScrollChildFram