Fix issue with Message.lua causing bot to crash (#290)

* Fix issue with Message.lua causing bot to crash

This fixes an issue with my friend's bot where `reaction` is nil and causes the bot to crash. The check should be before the definition of `reaction` to fix the issue.

* Apply fix for issue properly

I originally messed up and put the if statement higher when `reactions` was nil, and `reactions` was attempted to be indexed when nil, not `reaction` being nil.

* Apply requested changes

Makes the check for reactions an if statement rather than in-line with the variable.

libs/containers/Message.lua

@@ -122,11 +122,12 @@ end
 function Message:_removeReaction(d)
 
 	local reactions = self._reactions
-
+	if not reactions then return nil end
+
 	local emoji = d.emoji
 	local k = emoji.id ~= null and emoji.id or emoji.name
-	local reaction = reactions:get(k)
-
+	local reaction = reactions:get(k) or nil
+	
 	if not reaction then return nil end -- uncached reaction?
 
 	reaction._count = reaction._count - 1