Angular 8 :ERROR TypeError: Cannot read property 'invalid' of undefined

Can someone explain what this actually means? I am new to Angular and currently using Angular 8 and this appears on my console.

ERROR TypeError: Cannot read property 'invalid' of undefined

at Object.eval [as updateDirectives] (RegisterComponent.html:10)
at Object.debugUpdateDirectives [as updateDirectives] (core.js:45259)
at checkAndUpdateView (core.js:44271)
at callViewAction (core.js:44637)
at execComponentViewsAction (core.js:44565)
at checkAndUpdateView (core.js:44278)
at callViewAction (core.js:44637)
at execEmbeddedViewsAction (core.js:44594)
at checkAndUpdateView (core.js:44272)
at callViewAction (core.js:44637)

Here's my sourcode which implies the page that have the errors

register.component.ts

   import { authTkn } from './../shared/model/loginDetails';
   import { MahasiswaApiService } from './../shared/services/mahasiswa-api.service';
   import { Component, OnInit } from '@angular/core';
   import { Router, RouterModule } from '@angular/router';
   import { FormBuilder, FormGroup, Validators } from '@angular/forms';
   import { first } from 'rxjs/operators';
   import * as CryptoJS from 'crypto-js';
@Component({
  selector: 'app-register',
  templateUrl: './register.component.html',
  styleUrls: ['./register.component.scss']
})

export class RegisterComponent implements OnInit {

  public authTkn: authTkn = null;

  registerForm = this.fb.group({
    user_name: ['', Validators.required],
    fullname: ['', Validators.required],
    telepon: ['', Validators.required],
    email: ['', Validators.required],
    alamat: ['', Validators.required],
    birthdate: ['', Validators.required],
    foto_profil: ['', Validators.required],
    password: ['', Validators.required],
  });


constructor(private mahasiswaApi: MahasiswaApiService, private route: Router, private fb: FormBuilder) { }

ngOnInit() {
  }


onSubmit() {
    this.registerForm.controls.password.patchValue(
      CryptoJS.SHA512(this.registerForm.value.password).toString()
    );
    console.log(this.registerForm.value);
    this.mahasiswaApi.postUserRegister(this.registerForm.value).subscribe(
      res => {
        console.log(res);
        this.authTkn = res;
        console.log(this.authTkn);
        localStorage.setItem('token', this.authTkn.token);
        this.mahasiswaApi.getCurrentToken();
        this.route.navigate(['/home']);
        alert(this.authTkn.info);
      },
      error => {
        console.log(error);
        alert(error.error.message);
      }
    );
  }
}

register.component.html

<div class="login-form">
  <form [formGroup]="registerForm" (ngSubmit)="onSubmit()">
      <h2 class="text-center"> Register </h2>

      <!-- Register Username -->
      <div class="form-group">
          <label for="user_name"> Username </label>
          <input type="text" class="form-control" name="Username" formControlName="user_name" placeholder="text">
          <div class="alert alert-danger" *ngIf="user_name.invalid && user_name.dirty" @myInsertRemoveTrigger>Username Must Be filled</div>
      </div>

      <!-- Register Nama Lengkap -->
      <div class="form-group">
        <label for="nama lengkap"> Nama Lengkap </label>
        <input type="text" class="form-control" name="Nama Lengkap" formControlName="fullname" placeholder="text">
        <div class="alert alert-danger" *ngIf="fullname.invalid && fullname.dirty" @myInsertRemoveTrigger> Please fill your complete name here</div>
    </div>

      <!-- Register Nomor Telepon -->
      <div class="form-group">
        <label for="nomor_telepon"> Nomor Telepon </label>
        <input type="text" class="form-control" name="Nomor Telepon" formControlName="telepon" placeholder="text">
      </div>

    <!-- Register Email -->
    <div class="form-group">
      <label for="email"> Email </label>
      <input type="email" class="form-control" name="Email" formControlName="email" placeholder="email">
    </div>

    <!-- Register Tanggal Lahir -->
    <div class="form-group">
      <label for="Tanggal_lahir"> Tanggal Lahir </label>
      <input type="date" class="form-control" name="Tanggal Lahir" formControlName="birthdate" placeholder="date">
    </div>

    <!-- Register Foto -->
    <div class="form-group">
      <label for="Foto_Profil"> Foto Profil </label>
      <input type="file" class="form-control" name="Foto Profil" formControlName="foto_profil" placeholder="file">
    </div>

    <!-- Register Password -->
    <div class="form-group">
      <label for="Password"> Password </label>
      <input type="password" class="form-control" name="Password" formControlName="password" placeholder="password">
      <div class="alert alert-danger" *ngIf="password.invalid && password.dirty" @myInsertRemoveTrigger>Password Must Be filled</div>
  </div>


      <!-- Button shit -->
      <div class="form-group">
          <button type="submit" class="btn btn-primary btn-block" [disabled]="!registerForm.valid"> Register </button>
      </div>

      <div class="clearfix">
          <label class="pull-left checkbox-inline"><input type="checkbox" formControlName="remember_me"> Remember me</label>
      </div>
  </form>
</div>

Maybe I had some variable definition problem, but I did actually define arrays of used variables for my form at the first part of my ts. Maybe I did lost something, what is that?