How to fix error num_rows Property

Question

Folks I have a question regarding this error:

Notice: Trying to get Property 'num_rows' of non-object in C: xampp htdocs control inc database.php on line 94.

Follows part of the code.

function find( $table = null, $id_tag = null ) {            
    $database = open_database();        
    $found = null;          

    try {         
        if ($id_tag) {         
             $sql = "SELECT * FROM " . $table . " WHERE id= " . $id_tag;            
             $result = $database->query($sql);                      

             if ($result->num_rows > 0) {             
                 $found = $result->fetch_assoc();           
                }                     
            } else {                       
                 $sql = "SELECT * FROM " . $table;          
                $result = $database->query($sql);                       
             **if ($result->num_rows > 0) {           
                $found = $result->fetch_all(MYSQLI_ASSOC);**                            
                }        
             }      

         } catch (Exception $e) {         
            $_SESSION['message'] = $e->GetMessage();          
            $_SESSION['type'] = 'danger';     }             
            close_database($database);      
            return $found;  
}