What steps will reproduce the problem?
1. Get a fresh whisper tab (you can whisper yourself).
2. As soon as the new whisper tab shows up, you'll get the error.

What is the expected output? What do you see instead?
There should be a "glow" under the tab's name, but with MoveAnything installed the glow doesn't work, and the first time a whisper tab appears, an error pops up. Also, the glow never shows even for new whispers on already existing tabs.

Upon further investigation, looks like it happens only the first time someone whispers to you in a session (or interface reset). If you close that tab and you get new whispers from that same person, it won't give an error (until you reset the UI). The glow still doesn't show, though.

What version of the product are you using?
16.0.3 (happened with the 15.0.X as soon as the pre-patch hit the live servers).

Do you have an error log of what happened?
Message: ...ing\Libs\!NoTaint\Libs\LibChatAnims\LibChatAnims.lua:128: attempt to call method 'SetChange' (a nil value)
Time: 07/26/16 12:12:00
Count: 1
Stack: ...ing\Libs\!NoTaint\Libs\LibChatAnims\LibChatAnims.lua:128: in function `FCF_StartAlertFlash'
Interface\FrameXML\ChatFrame.lua:3222: in function `ChatFrame_MessageEventHandler'
Interface\FrameXML\ChatFrame.lua:2645: in function `ChatFrame_OnEvent'
[string "*:OnEvent"]:1: in function <[string "*:OnEvent"]:1>
Interface\FrameXML\FloatingChatFrame.lua:2514: in function <Interface\FrameXML\FloatingChatFrame.lua:2502>

Locals: chatFrame = ChatFrame11 {
0 = <userdata>
isUninteractable = false
flashTimer = 0
chatTarget = "Morben-C'Thun"
isTemporary = true
originalShow = <function> defined =[C]:-1
tellTimer = 318038.861
inUse = true
isRegistered = true
resizeButton = ChatFrame11ResizeButton {
}
buttonFrame = ChatFrame11ButtonFrame {
}
Hide = <function> defined @Interface\FrameXML\FrameLocks.lua:124
privateMessageList = <table> {
}
oldAlpha = 0
channelList = <table> {
}
buttonSide = "left"
clickAnywhereButton = ChatFrame11ClickAnywhereButton {
}
isDocked = 1
alternativeDefaultLanguage = "Lengua común"
editBox = ChatFrame11EditBox {
}
Show = <function> defined @Interface\FrameXML\FrameLocks.lua:128
isLocked = true
name = "Morben-C'Thun"
originalHide = <function> defined =[C]:-1
chatType = "WHISPER"
zoneChannelList = <table> {
}
defaultLanguage = "Lengua común"
messageTypeList = <table> {
}
}
chatTab = ChatFrame11Tab {
0 = <userdata>
leftHighlightTexture = ChatFrame11TabHighlightLeft {
}
middleHighlightTexture = ChatFrame11TabHighlightMiddle {
}
originalShow = <function> defined =[C]:-1
sizePadding = 10
rightHighlightTexture = ChatFrame11TabHighlightRight {
}
mouseOverAlpha = 0.6
glow = ChatFrame11TabGlow {
}
middleTexture = ChatFrame11TabMiddle {
}
Hide = <function> defined @Interface\FrameXML\FrameLocks.lua:124
rightSelectedTexture = ChatFrame11TabSelectedRight {
}
leftSelectedTexture = ChatFrame11TabSelectedLeft {
}
textWidth = 81.066665649414
originalHide = <function> defined =[C]:-1
Show = <function> defined @Interface\FrameXML\FrameLocks.lua:128
selectedColorTable = <table> {
}
middleSelectedTexture = ChatFrame11TabSelectedMiddle {
}
rightTexture = ChatFrame11TabRight {
}
noMouseAlpha = 0.2
alerting = false
conversationIcon = ChatFrame11TabConversationIcon {
}
leftTexture = ChatFrame11TabLeft {
}
}
fade1 = <unnamed> {
0 = <userdata>
}
(*temporary) = nil
(*temporary) = <unnamed> {
0 = <userdata>
}
(*temporary) = 1
(*temporary) = "attempt to call method 'SetChange' (a nil value)"
anims = <table> {
(null) = <unnamed> {
}
}

Please provide any additional information below.
I've tested this disabling every addon except for MoveAnything, and even removing its SavedVariables and the whole WTF folder and removing every addon from the AddOns folder except for MoveAnything. It always shows the error when getting a new whisper tab for the first time in a session.