refactor(zoe): Populate initialAllocation with empty want properties …

…before give properties

This currently has no significant effect because cleanProposal uses
assertKeywordNotInBoth to guarantee disjoint keywords, but we should not
overwrite give amounts when/if that constraint is removed.

packages/zoe/src/zoeService/escrowStorage.js

@@ -108,8 +108,10 @@ export const provideEscrowStorage = baggage => {
     const deposits = await deeplyFulfilledObject(depositPs);
 
     const initialAllocation = harden({
-      ...deposits,
       ...objectMap(want, amount => AmountMath.makeEmptyFromAmount(amount)),
+      // Deposits should win in case of overlapping give/want keywords
+      // (which are not allowed as of 2024-01).
+      ...deposits,
     });
 
     return initialAllocation;