i3 error

ERROR: CONFIG: Expected one of these tokens: <end>, '#', 'set', 'bindsym', 'bindcode', 'bind', 'bar', 'font', 'mode', 'floating_minimum_size', 'floating_maximum_size', 'floating_modifier', 'default_orientation', 'workspace_layout', 'new_window', 'new_float', 'hide_edge_borders', 'for_window', 'assign', 'no_focus', 'focus_follows_mouse', 'mouse_warping', 'force_focus_wrapping', 'force_xinerama', 'force-xinerama', 'workspace_auto_back_and_forth', 'fake_outputs', 'fake-outputs', 'force_display_urgency_hint', 'focus_on_window_activation', 'show_marks', 'workspace', 'ipc_socket', 'ipc-socket', 'restart_state', 'popup_during_fullscreen', 'exec_always', 'exec', 'client.background', 'client.focused_inactive', 'client.focused', 'client.unfocused', 'client.urgent', 'client.placeholder'
ERROR: CONFIG: (in file /home/piero/.config/i3/config)
ERROR: CONFIG: Line 175: bindsym XF86AudioPrev exec playerctl previous
ERROR: CONFIG: Line 176:
ERROR: CONFIG: Line 177:  smart_gaps on
ERROR: CONFIG:            ^^^^^^^^^^^^^
ERROR: CONFIG: Line 178:
ERROR: CONFIG: Line 179: bar {
ERROR: FYI: You are using i3 version 4.12 (2016-03-06, branch "4.12")
ERROR: Received ConfigureNotify for unknown window 0x01600000
ERROR: Received ConfigureNotify for unknown window 0x01600000
ERROR: Received ConfigureNotify for unknown window 0x01600003
ERROR: Received ExposeEvent for unknown window 0x01600003
ERROR: Received ConfigureNotify for unknown window 0x01600003
ERROR: Received ConfigureNotify for unknown window 0x01600003
ERROR: Received ExposeEvent for unknown window 0x01600003
ERROR: Received ConfigureNotify for unknown window 0x01600003