[BUGFIX] Fix exception if no value or description is set for the markers

Resources/Private/Templates/Mail/Index.html

@@ -14,16 +14,24 @@
 		<table class="table table-hover">
 			<thead>
 				<tr>
-					<th>{f:translate(key:'backend.marker')}</th>
-					<th>{f:translate(key:'backend.value')}</th>
-					<th>{f:translate(key:'backend.description')}</th>
+					<th><f:translate key="backend.marker" /></th>
+					<th><f:translate key="backend.value" /></th>
+					<th><f:translate key="backend.description" /></th>
 				</tr>
 			</thead>
 			<f:for each="{selectedTemplate.marker}" as="marker">
 				<tr>
 					<td>{marker.marker}</td>
-					<td><f:translate key="{marker.value}">{marker.value}</f:translate></td>
-					<td><f:translate key="{marker.description}">{marker.description}</f:translate></td>
+					<td>
+						<f:if condition="{marker.value}">
+							<f:translate key="{marker.value}">{marker.value}</f:translate>
+						</f:if>
+					</td>
+					<td>
+						<f:if condition="{marker.description}">
+							<f:translate key="{marker.description}">{marker.description}</f:translate>
+						</f:if>
+					</td>
 				</tr>
 			</f:for>
 		</table>