Hi I am using ONSUBMIT event for validating fields using below code. Unfortunately I am getting an error 

"[Cannot read property 'config' of undefined]"

<lightning:recordEditForm aura:id="recordViewForm"
                              objectApiName="Candidate__c"
                              recordId="{!v.recordId}"
                              recordTypeId=""
                              
                              onsubmit="{!c.onSubmit}"
                              onsuccess="{!c.handleSuccess}"
                              >
        <lightning:messages />

===================================================


<div class="slds-size_1-of-2 slds-max-small-size_1-of-1">
                       
                            <lightning:inputField aura:id="endDateOnProject" fieldName="End_Date_on_Project__c"/>
                    </div>
                    <div class="slds-size_1-of-2 slds-max-small-size_1-of-1">
                        <lightning:inputField aura:id="reasonProjectEnded" fieldName="Reason_Project_Ended__c"/>
                    </div>
                    <div class="slds-size_1-of-2 slds-max-small-size_1-of-1">
                        <lightning:inputField aura:id="DummyField1" fieldName="" />
                    </div>
                    <div class="slds-size_1-of-2 slds-max-small-size_1-of-1">
                        <lightning:inputField aura:id="Candidate-EndDate-NotifiedBy" fieldName="Candidate_EndDate_NotifiedBy__c" />
                    </div>

Controller:

onSubmit : function(component, event, helper) {
        
        var endDateProj = component.find("endDateOnProject");
        var endDateProjValue = endDateProj.get("v.value");
        console.log(endDateProj);
        var notifyBy = component.find("Candidate-EndDate-NotifiedBy");
        var notifyByValue = notifyBy.get("v.value");
        console.log(notifyByValue);
        if (endDateProjValue !== null){
            
            notifyBy.set("v.errors", [{"message":"Quantity can’t be blank."}]);
        }
        
    },

I am using code suggested by Salesforce Aura developer guide.

/*errorHandlingCustomController.js*/
{
    doAction : function(component, event) {
        var inputCmp = component.find("inputCmp");
        var value = inputCmp.get("v.value");

        // is input numeric?
        if (isNaN(value)) {
            inputCmp.set("v.errors", [{message:"Input not a number: " + value}]);
        } else {
            inputCmp.set("v.errors", null);
        }
    },

    handleError: function(component, event){
        /* do any custom error handling
         * logic desired here */
        // get v.errors, which is an Object[]
        var errorsArr  = event.getParam("errors");
        for (var i = 0; i < errorsArr.length; i++) {
            console.log("error " + i + ": " + JSON.stringify(errorsArr[i]));
        }
    },

    handleClearError: function(component, event) {
        /* do any custom error handling
         * logic desired here */
    }
}

I dont knew why i am getting this error.
please help me on this. Thanks in advance.​​​​​​​