Print an error when trying to open a dir as a file

Prevents unnecessary stack traces

lib/rex/post/meterpreter/ui/console/command_dispatcher/stdapi/fs.rb

@@ -124,6 +124,9 @@ class Console::CommandDispatcher::Stdapi::Fs
 			return true
 		end
 
+		if (client.fs.stat(args[0]).directory?)
+			print_error("#{args[0]} is a directory")
+		else
 			fd = client.fs.file.new(args[0], "rb")
 
 			until fd.eof?
@@ -131,6 +134,7 @@ class Console::CommandDispatcher::Stdapi::Fs
 			end
 
 			fd.close
+		end
 
 		true
 	end