Close taiga process before starting installation

[soredake]

Otherwise you will see this:

[erengy]

Installer does try to close Taiga by sending its main window a WM_DESTROY message and displays that message only if Taiga is still running after 3 seconds:

taiga/setup/Taiga.nsi

Lines 199 to 228 in b6f440e

	Function CheckInstance
	Var /GLOBAL messageSent
	StrCpy $messageSent "false"
	Var /GLOBAL secondsWaited
	IntOp $secondsWaited 0 + 0
	checkInstanceLoop:
	System::Call "kernel32::OpenMutex(i 0x100000, b 0, t '${PRODUCT_MUTEX}') i .R0"
	IntCmp $R0 0 skipInstanceCheck
	System::Call "kernel32::CloseHandle(i $R0)"
	IfSilent skipSendMessage ; Assuming the application is going to close itself
	StrCmp $messageSent "true" skipSendMessage
	FindWindow $R0 "TaigaMainW"
	SendMessage $R0 ${WM_DESTROY} 0 0
	StrCpy $messageSent "true"
	Goto skipMessageBox
	skipSendMessage:
	IntOp $secondsWaited $secondsWaited + 1
	IntCmp $secondsWaited 3 0 skipMessageBox 0 ; Display the message box after 3 seconds
	MessageBox MB_OKCANCEL|MB_ICONEXCLAMATION "${PRODUCT_NAME} is still running. Close it first, then click OK to continue setup." IDOK skipMessageBox
	Quit
	skipMessageBox:
	Sleep 1000
	Goto checkInstanceLoop
	skipInstanceCheck:
	FunctionEnd

I assume you're running the installer in silent mode, in which it skips sending the message due to #1123 (comment).