Property widget: Blank editor on multi-select

[dlew72]

Package
@itwin/property-grid-react

Describe the bug
When alwaysShowEditor is enabled and two similar elements are selected that have Varying properties, the property value appears blank.

To Reproduce
Steps to reproduce the behavior:

1. Have an iModel with two elements of the same class that have some properties that have different values
2. Have alwaysShowEditor enabled
3. Select both elements
4. See empty editors

Expected behavior
We expect that in the specific case that *** Varies *** would be shown normally (with alwaysShowEditor off), that *** Varies *** is still shown. Perhaps for those specific properties, it skirts around the alwaysShowEditor flag and doesn't show the editor until clicked.

Screenshots
In the screenshot below, you can see two Area Vertex elements selected in OpenSite+. Location and User Label are both set for each individual element. When multi-selected, the editor appears blank, which implies that they aren't set to anything.

Desktop (please complete the applicable information):
OS: Windows
Electron 36.9.1
iTwin.js 5.6.0

[grigasp]

This is a known issue and the fix will land into @itwin/presentation-components package: iTwin/presentation#1189.

Let's keep this one open to track integration of the fix into property widget & test viewer.

[MartynasStrazdas]

This seems like a dublicate or similar to of iTwin/presentation#1189