Fix Engine UI crash when chain is undefined | DASH-42 (#2654)

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## PR-Codex overview
This PR ensures optional chaining is used to access properties in various components, preventing errors when properties are undefined.

### Detailed summary
- Added optional chaining to access `chain` properties in multiple components
- Ensured safe access to `chain.explorers` and `chain.icon` properties

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src/components/engine/contract-subscription/contract-subscriptions-table.tsx

@@ -290,7 +290,7 @@ const RemoveModal = ({
               <FormControl>
                 <FormLabel>Chain</FormLabel>
                 <Flex align="center" gap={2}>
-                  <ChainIcon size={12} ipfsSrc={chain.icon?.url} />
+                  <ChainIcon size={12} ipfsSrc={chain?.icon?.url} />
                   <Text>{chain.name}</Text>
                 </Flex>
               </FormControl>

src/components/engine/overview/backend-wallets-table.tsx

@@ -141,7 +141,7 @@ const BackendWalletBalanceCell: React.FC<BackendWalletBalanceCellProps> = ({
     </Text>
   );
 
-  const explorer = chain.explorers?.[0];
+  const explorer = chain?.explorers?.[0];
   if (!explorer) {
     return balanceComponent;
   }

src/components/engine/relayer/relayers-table.tsx

@@ -71,7 +71,7 @@ export const RelayersTable: React.FC<RelayersTableProps> = ({
         const chain = chainIdToChainRecord[parseInt(cell.getValue())];
         return (
           <Flex align="center" gap={2}>
-            <ChainIcon size={12} ipfsSrc={chain.icon?.url} />
+            <ChainIcon size={12} ipfsSrc={chain?.icon?.url} />
             <Text>{chain.name}</Text>
           </Flex>
         );
@@ -83,7 +83,7 @@ export const RelayersTable: React.FC<RelayersTableProps> = ({
         const { chainId, backendWalletAddress } = cell.row.original;
         const chain = chainIdToChainRecord[parseInt(chainId)];
 
-        const explorer = chain.explorers?.[0];
+        const explorer = chain?.explorers?.[0];
         if (!explorer) {
           return backendWalletAddress;
         }