diff --git a/inc/User.class.php b/inc/User.class.php
index e6d4350..75f44f7 100644
--- a/inc/User.class.php
+++ b/inc/User.class.php
@@ -67,7 +67,11 @@ class User extends Storage {
     }
 
     public function setEmail($email) {
-        if(filter_var($email, FILTER_VALIDATE_EMAIL) !== false) {
+        if (empty($email)) {
+            $this->email = null;
+            return true;
+        }
+        elseif(filter_var($email, FILTER_VALIDATE_EMAIL) !== false) {
             $this->email = $email;
             return true;
         }
@@ -77,7 +81,7 @@ class User extends Storage {
     }
 
     public function setDisplayName($display_name) {
-        $this->display_name = $display_name;
+        $this->display_name = (!empty($display_name) ? $display_name : NULL);
     }
 
     public function setPassword($password) {
@@ -113,7 +117,7 @@ class User extends Storage {
     }
 
     public function setStaySignedInToken($token) {
-        $this->stay_signed_in_token = $token;
+        $this->stay_signed_in_token = (!empty($token) ? $token : NULL);
     }
 
     // Password functions
@@ -177,8 +181,18 @@ class User extends Storage {
     // (a user = a unique login and display_name)
     // =========================================
     public function isUnique() {
-        if($this->load(array('login'=>$this->login)) === false && $this->load(array('display_name'=>$this->display_name)) === false) {
-            return true;
+        if($this->load(array('login'=>$this->login)) === false) {
+            if (!empty($this->display_name)) {
+                if ($this->load(array('display_name'=>$this->display_name)) === false) {
+                    return true;
+                }
+                else {
+                    return false;
+                }
+            }
+            else {
+                return true;
+            }
         }
         else {
             return false;
diff --git a/index.php b/index.php
index 7334139..1c7e400 100644
--- a/index.php
+++ b/index.php
@@ -227,7 +227,7 @@
                         $user->setPassword($user->encrypt($_POST['password']));
                     }
                     $user->setAdmin($_POST['admin']);
-                    $user->setStaySignedInToken("");
+                    $user->setStaySignedInToken(NULL);
 
                     if($user->setEmail($_POST['email']) !== false) {
                         if(!empty($_POST['user_id']) || $user->isUnique()) {
@@ -1088,7 +1088,7 @@
 
                 // Only keep the invoices which concern the user (as buyer or user in) (only if user != admin)
                 // TODO : Optimize ?
-                if(!$current_user->getAdmin()) {
+                if(!$current_user->getAdmin() && $invoices_list !== false) {
                     foreach($invoices_list as $key=>$invoice) {
                         if($invoice->getBuyer() != $current_user->getId() && !$invoice->getUsersIn()->inUsersIn($current_user->getId())) {
                             unset($invoices_list[$key]);
diff --git a/tpl/default/index.html b/tpl/default/index.html
index 9d0e547..0b93d7b 100644
--- a/tpl/default/index.html
+++ b/tpl/default/index.html
@@ -35,7 +35,7 @@
             <tr>
                 <th>{$i18n['users']}</th>
                 <th>{$i18n['you_owe_him']}</th>
-                <th>{$i18n['he_owes_you']}/th>
+                <th>{$i18n['he_owes_you']}</th>
             </tr>
             {loop="$users"}
                 {if condition="$balances[$value->getId()][$current_user->getId()] !== 'X' && $balances[$value->getId()][$current_user->getId()] !== '-'"}
@@ -141,7 +141,7 @@
             {/loop}
         </table>
     {else}
-    <p class="center">{$i18n['no_bills']}.</p>
+    <p class="center">{$i18n['no_bills']}</p>
     {/if}
 </div>
 {include="footer"}