fix fetchUserPositions should use window.adrena.client.readonlyConnec…

…tion

although the user positions are only fetched after user's wallet is connected,
the AdrenaClient.connection (from the user-scoped program's provider attached to the client),
may not yet be available.

this is fine because we still have the read-only program available, we can fetch positions.

src/actions/thunks.ts

@@ -113,7 +113,7 @@ export const fetchUserPositions =
     dispatch: Dispatch,
     getState: () => RootState,
   ): Promise<Array<PositionExtended> | null> => {
-    const connection = window.adrena.client.connection;
+    const connection = window.adrena.mainConnection;
     const walletPublicKey = selectWalletPublicKey(getState());
     const possibleUserPositions = selectPossibleUserPositions(getState());