fix: misspelled word (cloudevents#113)

Signed-off-by: Helio Frota <[email protected]>

Author: helio-frota

lib/formats/json/parser.js

@@ -6,7 +6,7 @@ const {
 
 const invalidPayloadTypeError =
   new Error("invalid payload type, allowed are: string or object");
-const nullOrIndefinedPayload =
+const nullOrUndefinedPayload =
   new Error("null or undefined payload");
 
 const asJSON = (v) => (isString(v) ? JSON.parse(v) : v);
@@ -28,7 +28,7 @@ class JSONParser {
 
     return Array.of(payload)
 
-      .filter((p) => isDefinedOrThrow(p, nullOrIndefinedPayload))
+      .filter((p) => isDefinedOrThrow(p, nullOrUndefinedPayload))
       .filter((p) => isStringOrObjectOrThrow(p, invalidPayloadTypeError))
       .map(asJSON)
       .shift();