Quite often, when upgrading Moodle like this:
I was upgrade my moodle from 2.8 to 3.2
That is a spread of 2.9,3.0 3.1 and 3.2, a rather large jump. I can't say for sure, but AFAIK, there are often minor updates to things that can mean larger updates over a larger set of versions. So the question becomes did you do an update or did you do an upgrade?
[My definitions of the two are the update is run and where files are the same, they are not changed, only files that are different are changed (assuming that compilation dates are used as criteria for what's changed). An upgrade means the codebase is entirely deleted except for the config.php file which is copied back to the /moodle directory when the new code is pasted. ]
If you did an update, the error is a likely outcome of coding changes in the way the array is called and/or the location of the called routine. BUT, IANAD, so I am posssibly right off track here.
You might want to consider an upgrade every year though, even if you are one version behind the latest release, you will stay relatively current.