Using: SNAPSHOT_v11.1d_2017-04-18 (2017-04-18)
In the Docs (and the referenceDocs.xml file) the getDisplayValue() method of ListGrid is specified to return a string. Sometimes, however, it does not. Presumably this happens when the actual value which is not a string (like a number) cannot be mapped to a string display value. But, since the spec says it returns a string, it should still return a string. Recommend doing a .toString() before the value is returned or specify the return as any.
In the Docs (and the referenceDocs.xml file) the getDisplayValue() method of ListGrid is specified to return a string. Sometimes, however, it does not. Presumably this happens when the actual value which is not a string (like a number) cannot be mapped to a string display value. But, since the spec says it returns a string, it should still return a string. Recommend doing a .toString() before the value is returned or specify the return as any.