I am reposting this post that I found on Dejan Dular‘s blog.
That bug almost made me crazy. After two hours of Javascript debugging I finally realized what was going on and when I entered the right keywords in Google, I found that post:
I encountered a strange behavior after upgrading on premise CRM 2015 to 2016 version.
In the account form after I set the value of the custom lookup field (lookup to custom Country entity) I got javascript error:
SCRIPT5007: Unable to get property ‘trim’ of undefined or null reference
After some hours of debugging I removed all javascript code. Then I copied the example from SDK, the error was still there.
Investigating the setValue method I discovered, that something like “internalOnChange” was called. I suspect this method was called because there are some filtered lists in the page that depend on the value of this field.
Long story short, there are two ways to fix this:
Method 1:
Go to Settings-Administration-System settings. All the way down at the end of the page enable “Use legacy form rendering”.
This will definitely slow down form loading.
Method 2:
The code deep down in the out-of-the-box CRM javascript libraries the script wants to parse the attribute type, but it is not there. The value should be “lookup” and you should pass it in the object when calling setValue.
In addition, this error pop-uped in the console: Uncaught TypeError: Cannot read property ‘UnselectRecords’ of null.
In the end, I was able to update a field on the OnLoad event of a subgrid.