bp_assign_default_member_type_to_activate_user( $user_id,  $key,  $user )

function bp_assign_default_member_type_to_activate_user( $user_id, $key, $user ) {
	global $bp;

	// Check whether member type is enabled.
	if ( true === bp_member_type_enable_disable() ) {

		// return to user if default member type is not set.
		$existing_selected = bp_member_type_default_on_registration();
		if ( '' === $existing_selected ) {
			return;
		}

		$email = bp_core_get_user_email( $user_id );

		// Check if invites component enabled.
		if ( bp_is_active( 'invites' ) ) {
			$inviters = array();

			$args = array(
				'post_type'      => bp_get_invite_post_type(),
				'posts_per_page' => - 1,
				'meta_query'     => array(
					array(
						'key'     => '_bp_invitee_email',
						'value'   => $email,
						'compare' => '=',
					),
				),
			);

			$bp_get_invitee_email = new WP_Query( $args );

			if ( $bp_get_invitee_email->have_posts() ) {

				$member_type = get_post_meta( get_the_ID(), '_bp_invitee_member_type', true );
				// Check if user is invited for specific member type
				if ( isset( $member_type ) && ! empty( $member_type ) ) {
					// Assign the invited member type to user.
					bp_set_member_type( $user_id, '' );
					bp_set_member_type( $user_id, $member_type );
				} else {
					// Assign the default member type to user.
					bp_set_member_type( $user_id, '' );
					bp_set_member_type( $user_id, $existing_selected );
				}
				// If user is not invited by send invites then assign default member type.
			} else {
				// Assign the default member type to user.
				bp_set_member_type( $user_id, '' );
				bp_set_member_type( $user_id, $existing_selected );
			}
		} else {
			// Assign the default member type to user.
			bp_set_member_type( $user_id, '' );
			bp_set_member_type( $user_id, $existing_selected );
		}
	}

}