OnStyle callback is never called (confirmed also in the example file)

**[CustomStyle.lua](https://github.com/dail8859/LuaScript/blob/a4dd230779d099f16962bc4c00f465a7d58e36d9/examples/StyleCustom.lua) example file**

```lua
--[[ An example file

proc clip(int a)
« Clip into the positive zone »
if (a > 0) a
0
end
]]

-- Define style numbers
S_DEFAULT = 0
S_IDENTIFIER = 1
S_KEYWORD = 2
S_UNICODECOMMENT = 3

-- Anytime a file is switched, check to see if it needs styled
npp.AddEventHandler("OnSwitchFile", function(filename, bufferid)
if npp:GetExtPart() == ".abc" then
-- Add the event handler for our custom style function
npp.AddEventHandler("OnStyle", CustomStyle)

-- Make sure to set the lexer as a custom container
editor.Lexer = SCLEX_CONTAINER

-- Set up the styles as appropriate
editor.StyleFore[S_DEFAULT] = 0x7f007f
editor.StyleBold[S_DEFAULT] = true
editor.StyleFore[S_IDENTIFIER] = 0x000000
editor.StyleFore[S_KEYWORD] = 0x800000
editor.StyleBold[S_KEYWORD] = true
editor.StyleFore[S_UNICODECOMMENT] = 0x008000
editor.StyleFont[S_UNICODECOMMENT] = "Georgia"
editor.StyleItalic[S_UNICODECOMMENT] = true
editor.StyleSize[S_UNICODECOMMENT] = 9

-- Clear any style and re-lex the entire document
editor:ClearDocumentStyle()
editor:Colourise(0, -1)
else
-- Can remove the handler if it's not needed
npp.RemoveEventHandler("OnStyle", CustomStyle)
end

return false
end)

-- Style the document. Handles UTF-8 characters
function CustomStyle(styler)
identifierCharacters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"

styler:StartStyling(styler.startPos, styler.lengthDoc, styler.initStyle)
while styler:More() do
-- Exit state if needed
if styler:State() == S_IDENTIFIER then
if not identifierCharacters:find(styler:Current(), 1, true) then
identifier = styler:Token()
if identifier == "if" or identifier == "end" then
styler:ChangeState(S_KEYWORD)
end
styler:SetState(S_DEFAULT)
end
elseif styler:State() == S_UNICODECOMMENT then
if styler:Match("»") then
styler:ForwardSetState(S_DEFAULT)
end
end

-- Enter state if needed
if styler:State() == S_DEFAULT then
if styler:Match("«") then
styler:SetState(S_UNICODECOMMENT)
elseif identifierCharacters:find(styler:Current(), 1, true) then
styler:SetState(S_IDENTIFIER)
end
end

styler:Forward()
end
styler:EndStyling()
end
```

1. This source defines a function for callback `OnSwitchFile`. It declares to call `CustomStyle` for the event `OnStyle` if the file extension is `abc`.
2. My understanding is that ``editor:Colourise(0, -1)`` should lead to invocation of callback `OnStyle`.
3. Handling the callback ``OnStyle`` and thus calling `CustomStyle` should colorize the document as a consequence.
4. By adding `print()` statements and opening the Lua Console, one can observe which functions are actually run.

**Expected behavior:**

1. Callback `OnSwitchFile` is handled.
2. Callback `OnStyle` is handled.

**Actual behavior:**

1. Callback `OnSwitchFile` is handled.
2. Callback `OnStyle` is never handled, thus the function `CustomStyle` is never called.

This can be confirmed by the resulting styling. The given example document (stored with a filepath ending with `.abc`) leads to the following coloring:


This coloring (every foreground text color is purple) can be explained by the ``editor.StyleFore[S_DEFAULT] = 0x7f007f`` which is run and sets the default color to purple. But the actual styling function `CustomStyle` is not run.

**Environment:**

* Windows 10
* LuaScript v0.12 (64 bit). Lua 5.3.5
* Seems like the OnStyle handling should be triggered [here](https://github.com/dail8859/LuaScript/blob/a4dd230779d099f16962bc4c00f465a7d58e36d9/src/LuaScript.cpp#L308) but SCN_STYLENEEDED does not seem to be a received Scintilla notification.