MySQL ISNULL with INNER JOIN

Question

I have 2 tables: "shares" and "pending_share_changes". The "shares" table has the following columns:

share_ID, asset_ID, member_ID, percent_owner, is_approved

pending_share_changes has the following columns:

share_change_ID, asset_ID, member_ID, percent_owner, is_approved, requested_by

I have a form (php) which lists the pending changes which the members have to approve or deny. Everything works fine unless the member has no existing shares, which means there is no record in the "shares" table for them. The query I am using to view the pending share changes is as follows:

SELECT p.share_change_ID, assets.asset_desc, assets.asset_value, shares.percent_owner AS 
          percent_owner_old, p.percent_owner 
          FROM pending_share_changes as p
          inner join assets on assets.asset_ID = p.asset_ID
          inner join shares on shares.asset_ID = p.asset_ID AND shares.member_ID = p.member_ID
          INNER JOIN orgs ON orgs.org_ID = assets.org_ID
          WHERE orgs.org_ID = '$org_ID' AND p.member_ID = '$member_ID' AND p.is_approved = '0'

I tried using IFNULL(shares.percent_owner, 0) AS percent_owner_old but that didn't work. The query returns no results. I would like to have the percent_owner_old column display a "0" if there is no record in the shares table.

Thanks.