BugGrabber: Restrict fetchFromDatabase() to current game session only

[2072]

Just thought I switched to the fifth dimension today because fetchFromDatabase() fetches stack-traces from all sessions and thus can report non-existing stack-traces involving removed add-ons...

This can make debugging very difficult or even impossible if one doesn't come to suspect a bug in BugGrabber itself...

Changing fetchFromDatabase() to the following in BugGrabber.lua fixes the problem:

local function fetchFromDatabase(database, target)

        local currentSessionId =  addon:GetSessionId()

	for i, err in next, database do
		if err.message == target and err.session == currentSessionId then
			-- This error already exists
			err.counter = err.counter + 1

			return table.remove(database, i)
		end
	end
end