fix(overmind): remove hot reloaded key when undefined

Author: christianalfoni

packages/node_modules/overmind/src/utils.ts

@@ -78,6 +78,11 @@ export function mergeState(originState, oldState, nextState) {
       return old
     }
 
+    // If we remove a key we return undefined to remove it
+    if (next === undefined) {
+      return next
+    }
+
     // If we have changed a state from origin, keep that
     // changed state
     if (next === origin && old !== origin) {