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$options = get_option( 'chec_settings' );
//Error message on line bellow
if ( is_array( $options ) && $options['chec_checkbox_field_0'] == '1' ) {
    echo 'Checked';
} else {
    echo 'Unchecked';
}

it the value is not checked it will not saved it db. so check if the $options is array.