Problem with PHP

Question

I am developing a small database to store some things, after done the schedules I came up with an error whose I can’t see your solution, could someone provide me help?

Error message:

Warning: mysqli_fetch_assoc() expects Parameter 1 to be mysqli_result, Boolean Given in C: wamp64 www Aula index.php on line 62

Code of the index:

Modal

List Courses

Register Register Course Name: Details: Register

        <div class="row">
            <div class="col-md-12">
                <table class="table">
                    <thead>
                        <tr>
                            <th>#</th>
                            <th>Nome do Curso</th>
                            <th>Ação</th>
                        </tr>
                    </thead>
                    <tbody>
                        <?php while($rows_cursos = mysqli_fetch_assoc($resultado_cursos)){ ?>
                            <tr>
                                <td><?php echo $rows_cursos['id']; ?></td>
                                <td><?php echo $rows_cursos['nome']; ?></td>
                                <td>
                                    <button type="button" class="btn btn-xs btn-primary" data-toggle="modal" data-target="#myModal<?php echo $rows_cursos['id']; ?>">Visualizar</button>

                                    <button type="button" class="btn btn-xs btn-warning" data-toggle="modal" data-target="#exampleModal" data-whatever="<?php echo $rows_cursos['id']; ?>" data-whatevernome="<?php echo $rows_cursos['nome']; ?>"  data-whateverdetalhes="<?php echo $rows_cursos['detalhes']; ?>">Editar</button>

                                    <a href="processa_apagar.php?id=<?php echo $rows_cursos['id']; ?>"><button type="button" class="btn btn-xs btn-danger">Apagar</button></a>
                                </td>
                            </tr>
                            <!-- Inicio Modal -->
                            <div class="modal fade" id="myModal<?php echo $rows_cursos['id']; ?>" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
                                <div class="modal-dialog" role="document">
                                    <div class="modal-content">
                                        <div class="modal-header">
                                            <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span></button>
                                            <h4 class="modal-title text-center" id="myModalLabel"><?php echo $rows_cursos['nome']; ?></h4>
                                        </div>
                                        <div class="modal-body">
                                            <p><?php echo $rows_cursos['id']; ?></p>
                                            <p><?php echo $rows_cursos['nome']; ?></p>
                                            <p><?php echo $rows_cursos['detalhes']; ?></p>
                                        </div>
                                    </div>
                                </div>
                            </div>
                            <!-- Fim Modal -->
                        <?php } ?>
                    </tbody>
                 </table>
            </div>
        </div>      
    </div>



    <div class="modal fade" id="exampleModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel">
        <div class="modal-dialog" role="document">
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span></button>
                    <h4 class="modal-title" id="exampleModalLabel">Cursos</h4>
                </div>
                <div class="modal-body">
                    <form method="POST" action="http://localhost/Aula/processa.php" enctype="multipart/form-data">
                        <div class="form-group">
                            <label for="recipient-name" class="control-label">Nome:</label>
                            <input name="nome" type="text" class="form-control" id="recipient-name">
                        </div>
                        <div class="form-group">
                            <label for="message-text" class="control-label">Detalhes:</label>
                            <textarea name="detalhes" class="form-control" id="detalhes-text"></textarea>
                        </div>
                        <input name="id" type="hidden" id="id_curso">
                        <div class="modal-footer">
                            <button type="button" class="btn btn-primary" data-dismiss="modal">Cancelar</button>
                            <button type="submit" class="btn btn-danger">Alterar</button>
                        </div>
                    </form>
                </div>            
            </div>
        </div>
    </div>





    <!-- jQuery (necessary for Bootstrap's JavaScript plugins) -->
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
    <!-- Include all compiled plugins (below), or include individual files as needed -->
    <script src="js/bootstrap.min.js"></script>
    <script type="text/javascript">
        $('#exampleModal').on('show.bs.modal', function (event) {
            var button = $(event.relatedTarget) // Button that triggered the modal
            var recipient = button.data('whatever') // Extract info from data-* attributes
            var recipientnome = button.data('whatevernome')
            var recipientdetalhes = button.data('whateverdetalhes')
            // If necessary, you could initiate an AJAX request here (and then do the updating in a callback).
            // Update the modal's content. We'll use jQuery here, but you could use a data binding library or other methods instead.
            var modal = $(this)
            modal.find('.modal-title').text('ID do Curso: ' + recipient)
            modal.find('#id_curso').val(recipient)
            modal.find('#recipient-name').val(recipientnome)
            modal.find('#detalhes-text').val(recipientdetalhes)
        })
    </script>
</body>