fix(overmind): fix rehydrate finding classes

Author: christianalfoni

packages/node_modules/overmind/src/rehydrate.ts

@@ -70,7 +70,7 @@ export const rehydrate = <T extends StateNode>(state: T, source: IMutation[] | S
       const pathArray = mutation.path.split(mutation.delimiter)
       const key = pathArray.pop() as string
       const target = pathArray.reduce((aggr, key) => aggr[key], state as any)
-      const classInstance = pathArray.reduce((aggr, key) => aggr[key], classes as any)
+      const classInstance = pathArray.reduce((aggr, key) => aggr && aggr[key], classes as any)
 
       if (mutation.method === 'set') {
         if (typeof classInstance === 'function' && Array.isArray(mutation.args[0])) {