Warning
JInstaller: :Install: Error SQL Can't DROP 'idx_image'; check that column/key exists
Files Update: SQL error file DB function failed with error number 1091
Can't DROP 'idx_image'; check that column/key exists
SQL =
ALTER TABLE #__languages DROP INDEX idx_image;
Although it's strange that the idx_image index did not exist I wouldn't be too concerned about it. That warning is essentially telling you that Joomla tried to get rid of something but it was already gone. The Joomla update was still successful.
I recommend that you go to (from your Joomla Administrator) Extensions > Manage > Database and confirm that there aren't any issues. If there are, the "fix" button should fix them for you.
Otherwise, you should be OK, unless you have a high-traffic site, or are noticing slow page load. I say this because if you had one missing database index you may have other missing database indexes (and I don't think the database check I recommended you do checks for missing indexes, but I could be wrong). That could result in slow query execution.
