Bug 1584576 - Prevent error in inline preview action r=jlast

Differential Revision: https://phabricator.services.mozilla.com/D47457

--HG--
extra : moz-landing-system : lando

devtools/client/debugger/src/actions/pause/inlinePreview.js

@@ -206,7 +206,11 @@ function getExpressionNameAndValue(
         );
         displayValue = property && property.contents.value;
         displayName += `.${meta.property}`;
-      } else if (displayValue && displayValue.preview) {
+      } else if (
+        displayValue &&
+        displayValue.preview &&
+        displayValue.preview.ownProperties
+      ) {
         const { ownProperties } = displayValue.preview;
         Object.keys(ownProperties).forEach(prop => {
           if (prop === meta.property) {