Default timeoutMs to low pri expiration if not provided

This is a required argument in the type signature but people may not
supply it and this is a user facing object.

Author: sebmarkbage

packages/react-reconciler/src/ReactFiberScheduler.js

@@ -274,7 +274,7 @@ export function computeExpirationForFiber(
     // Compute an expiration time based on the Suspense timeout.
     expirationTime = computeSuspenseExpiration(
       currentTime,
-      suspenseConfig.timeoutMs | 0,
+      (suspenseConfig.timeoutMs | 0) || LOW_PRIORITY_EXPIRATION,
     );
   } else {
     // Compute an expiration time based on the Scheduler priority.
@@ -1028,7 +1028,7 @@ function inferTimeFromExpirationTime(
   return (
     earliestExpirationTimeMs -
     (suspenseConfig !== null
-      ? suspenseConfig.timeoutMs | 0
+      ? (suspenseConfig.timeoutMs | 0) || LOW_PRIORITY_EXPIRATION
       : LOW_PRIORITY_EXPIRATION)
   );
 }