feat: add Arbitrum onchain space to Tally statement importer (#637)

Adds the Arbitrum Core Governor SX space to the Tally MAPPING so that
delegate statements imported from Tally are stored against the onchain
space and surfaced in the SX UI.

Also fixes a crash when Tally returns a delegate with no statement
(null instead of an empty object).

Author: ChaituVR

src/lib/importer/statement/provider/tally.ts

@@ -49,6 +49,7 @@ const ORGANIZATION_QUERY = {
 export default class Tally extends Provider {
   static readonly MAPPING = {
     's:arbitrumfoundation.eth': 'arbitrum',
+    'arb1:0x789fC99093B09aD01C34DC7251D0C89ce743e5a4': 'arbitrum',
     's:uniswapgovernance.eth': 'uniswap',
     's:dopedao.eth': 'dopewars',
     's:opcollective.eth': 'optimism',
@@ -108,7 +109,7 @@ export default class Tally extends Provider {
 
       const _delegates: Delegate[] = [];
       results.delegates.nodes.forEach((node: any) => {
-        const statement = node.statement.statement.trim();
+        const statement = node.statement?.statement?.trim();
 
         if (!statement) return;