Trying to access array offset on value of type null

Assalamualaikum Warahmatullahi Wabarakatuh... mohon bantuannya kakak-kakak, jadi saya mau menampilkan data dari database tapi muncul pesan error Trying to access array offset on value of type null. Kira-kira itu kesalahannya apa ya? Terimakasih
 
Controller saya :
<?php public function change_profile()
	{
		helper(['form', 'url']);
		$userModel = new UserModel();
 
		if ($this->request->getMethod() == 'post') {
			$rules = [
				'nama' 				=> 'required|alpha_space|min_length[2]',
				'nip'               => 'required|min_length[2]',
			];
 
			if ($this->validate($rules)) {
				$params = [
					'nama' 		=> $userModel->escapeString(esc($this->request->getPost('nama'))),
					'nip' => $userModel->escapeString(esc($this->request->getPost('nip'))),
 
				];
 
				$user = $userModel->where('email', session()->get('email'))
						->first();
 
				$update = $userModel->update($user['id_user'], $params);
 
				if ($update) {
					session()->setFlashdata('success', 'Berhasil Update Profile. Apabila Tampilan Data Belum Berubah, Silakan Lakukan Logout dan Login Kembali');
					return redirect()->route('admin/user/change_profile');
				} else {
					session()->setFlashdata('danger', 'Gagal edit data');
					return redirect()->route('admin/user/change_profile')->withInput();
				}
			} else {
				$data['validation'] = $this->validator;
			}
		}
 
		$data['title'] = 'Edit Biodata';
		$data['user'] = $userModel->where('id_user')->first();
 
		return view('admin/users/profile', $data);
	} ?>
 
View Saya :
<?php <form action="<?= base_url('admin/user/change_profile') ?>" method="POST" enctype="multipart/form-data">
    					<?= csrf_field(); ?>
						<form>
							<div class="form-row">
								<div class="form-group col-md-6">
									<label for="nama"><font face="Arial" size="2">Nama</font></label>
									<input type="text" class="form-control" name="nama" id="nama" value="<? $user['nama'] ?>" >
								</div>
 
								<div class="form-group col-md-6">
									<label for="nip"><font face="Arial" size="2">NIP</font></label>
									<input type="number" class="form-control" name="nip" id="nip" value="<?= $user['nip'] ?>" >
								</div>
 
						        </div>
						        <input type="submit" value="Update" class="btn btn-info"/>
 
						</form>		
				    </form> 
?>