set field description to undefined if not in config to better conform to type

Author: christensenemc

src/mutation/mutation.js

@@ -58,13 +58,9 @@ type MutationConfig = {
 export function mutationWithClientMutationId(
   config: MutationConfig
 ): GraphQLFieldConfig {
-  var {
-    name,
-    inputFields,
-    outputFields,
-    mutateAndGetPayload,
-    description
-  } = config;
+  var { name, inputFields, outputFields, mutateAndGetPayload } = config;
+
+  var description = config.description ? config.description : undefined;
   var augmentedInputFields = () => ({
     ...resolveMaybeThunk(inputFields),
     clientMutationId: {
@@ -88,7 +84,7 @@ export function mutationWithClientMutationId(
     fields: augmentedInputFields
   });
 
-  return {
+  var mutationField = {
     type: outputType,
     description: description,
     args: {
@@ -101,4 +97,6 @@ export function mutationWithClientMutationId(
       });
     }
   };
+
+  return mutationField;
 }