remove the concept of a main context

app closes when all contexts close now

src/funfriend.cr

@@ -28,17 +28,15 @@ module Funfriend
   LOG = ::Log.for("")
 
   @@contexts = [] of WindowContext
-  @@main_context : WindowContext?
 
   def self.should_close?
-    @@main_context && @@main_context.not_nil!.window.should_close?
+    @@contexts.size == 0
   end
 
   def self.init_contexts
     ConfigMan.config["buddies"]["types"].as(String).split(",").each do |buddy_name|
       add_context(BuddyContext.new(make_buddy(buddy_name)))
     end
-    @@main_context = @@contexts[0]
     at_exit { contexts.each &.destroy }
   end