[Explorer]: Fix error render on Object page (#13851)

## Description 

- Fix error rendering for Object page

BEFORE
<img width="865" alt="Screenshot 2023-09-19 at 12 03 17 PM"
src="https://github.com/MystenLabs/sui/assets/127577476/08d647f4-4f30-40b3-b4f2-f10daee19c25">

AFTER

<img width="811" alt="Screenshot 2023-09-19 at 12 03 21 PM"
src="https://github.com/MystenLabs/sui/assets/127577476/13395dfe-6e1f-4bb1-bcaf-2df1e72eb7a7">


## Test Plan 

How did you test the new or updated feature?

---
If your changes are not user-facing and not a breaking change, you can
skip the following section. Otherwise, please indicate what changed, and
then add to the Release Notes section as highlighted during the release
process.

### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

apps/explorer/src/pages/object-result/views/ObjectView.tsx

@@ -228,6 +228,8 @@ export function ObjectView({ data }: ObjectViewProps) {
 	const objectType = parseObjectType(data);
 	const objOwner = data.data?.owner;
 	const storageRebate = data.data?.storageRebate;
+	const objectId = data.data?.objectId;
+	const lastTransactionBlockDigest = data.data?.previousTransaction;
 
 	const heroImageTitle = name || display?.description || trimStdLibPrefix(objectType);
 	const heroImageSubtitle = video ? 'Video' : fileType ?? '';
@@ -257,18 +259,22 @@ export function ObjectView({ data }: ObjectViewProps) {
 				</div>
 			)}
 
-			<div style={{ gridArea: 'description' }}>
-				<DescriptionCard
-					name={name}
-					objectType={objectType}
-					objectId={data.data?.objectId!}
-					display={display}
-				/>
-			</div>
+			{objectId && (
+				<div style={{ gridArea: 'description' }}>
+					<DescriptionCard
+						name={name}
+						objectType={objectType}
+						objectId={objectId}
+						display={display}
+					/>
+				</div>
+			)}
 
-			<div style={{ gridArea: 'version' }}>
-				<VersionCard version={data.data?.version} digest={data.data?.previousTransaction!} />
-			</div>
+			{lastTransactionBlockDigest && (
+				<div style={{ gridArea: 'version' }}>
+					<VersionCard version={data.data?.version} digest={lastTransactionBlockDigest} />
+				</div>
+			)}
 
 			<div style={{ gridArea: 'owner' }}>
 				<OwnerCard objOwner={objOwner} display={display} storageRebate={storageRebate} />

apps/explorer/src/ui/PageHeader.tsx

@@ -61,14 +61,18 @@ export function PageHeader({ title, subtitle, type, before, error, loading }: Pa
 							{loading ? (
 								<Placeholder rounded="lg" width="540px" height="20px" />
 							) : (
-								<div className="flex items-center">
-									<Heading as="h3" variant="heading3/semibold" color="gray-90" mono>
-										{title}
-									</Heading>
-									<div className="ml-2 h-4 w-4 self-start md:h-6 md:w-6">
-										<CopyToClipboard size="lg" color="steel" copyText={title} />
-									</div>
-								</div>
+								<>
+									{title && (
+										<div className="flex items-center">
+											<Heading as="h3" variant="heading3/semibold" color="gray-90" mono>
+												{title}
+											</Heading>
+											<div className="ml-2 h-4 w-4 self-start md:h-6 md:w-6">
+												<CopyToClipboard size="lg" color="steel" copyText={title} />
+											</div>
+										</div>
+									)}
+								</>
 							)}
 						</div>
 						{subtitle && (