Changed tests and tools to use 'discard' statements instead of 'nil' for empty blocks.

tests/stdlib/tircbot.nim

@@ -183,7 +183,7 @@ type
     channel: string
     timestamp: TTime
     case kind*: TSeenType
-    of PSeenJoin: nil
+    of PSeenJoin: discard
     of PSeenPart, PSeenQuit, PSeenMsg:
       msg: string
     of PSeenNick:
@@ -200,7 +200,7 @@ proc setSeen(d: TDb, s: TSeen) =
   var hashToSet = @[("type", $s.kind.int), ("channel", s.channel),
                     ("timestamp", $s.timestamp.int)]
   case s.kind
-  of PSeenJoin: nil
+  of PSeenJoin: discard
   of PSeenPart, PSeenMsg, PSeenQuit:
     hashToSet.add(("msg", s.msg))
   of PSeenNick:
@@ -338,7 +338,7 @@ proc hubConnect(state: PState) =
 
 proc handleIrc(irc: PAsyncIRC, event: TIRCEvent, state: PState) =
   case event.typ
-  of EvConnected: nil
+  of EvConnected: discard
   of EvDisconnected:
     while not state.ircClient.isConnected:
       try:
@@ -424,7 +424,7 @@ proc handleIrc(irc: PAsyncIRC, event: TIRCEvent, state: PState) =
       seenNick.newNick = event.params[0]
       state.database.setSeen(seenNick)
     else:
-      nil # TODO: ?
+      discard # TODO: ?
 
 proc open(port: TPort = TPort(5123)): PState =
   var res: PState