fix: Use a local variable to ensure connection is not nil (#53)

src/bojack/console.cr

@@ -3,6 +3,8 @@ require "bojack-client"
 
 module BoJack
   class Console
+    @client : BoJack::Client?
+
     def initialize(@hostname : String = "127.0.0.1", @port : Int8 | Int16 | Int32 | Int64 = 5000)
       begin
         @client = BoJack::Client.new(@hostname, @port)
@@ -13,9 +15,11 @@ module BoJack
     end
 
     def start
+      client = @client
+      return unless client
       loop do
         input = Readline.readline("> ", true)
-        puts @client.send(input)
+        puts client.send(input)
         break if input == "close"
       end
     end