use isset to check existance of a variable

git-svn-id: https://svn.code.sf.net/p/postfixadmin/code/trunk@1238 a1433add-5e2c-0410-b055-b7f2511e0802

templates/flash_error.tpl

@@ -1,15 +1,15 @@
 <!-- {$smarty.template} -->
 <br clear="all"/><br />
 {strip}
-		{if $smarty.session.flash}
-			{if $smarty.session.flash.info}
+		{if isset($smarty.session.flash)}
+			{if isset($smarty.session.flash.info)}
 				<ul class="flash-info">
 					{foreach from=$smarty.session.flash.info item=msg}
 						<li>{$msg}</li>
 					{/foreach}
 				</ul>
 			{/if}
-			{if $smarty.session.flash.error}
+			{if isset($smarty.session.flash.error)}
 				<ul class="flash-error">
 					{foreach from=$smarty.session.flash.error item=msg}
 						<li>{$msg}</li>
@@ -17,4 +17,4 @@
 				</ul>
 			{/if}
 		{/if}
-{/strip}
+{/strip}