Bug 300006: "cookies need value" error code when a query returns an empty result.

buglist.cgi

@@ -1013,7 +1013,10 @@ if ($format->{'extension'} eq "html") {
     }
     my $bugids = join(":", @bugidlist);
     # See also Bug 111999
-    if (length($bugids) < 4000) {
+    if (length($bugids) == 0) {
+        $cgi->remove_cookie('BUGLIST');
+    }
+    elsif (length($bugids) < 4000) {
         $cgi->send_cookie(-name => 'BUGLIST',
                           -value => $bugids,
                           -expires => 'Fri, 01-Jan-2038 00:00:00 GMT');

colchange.cgi

@@ -103,9 +103,14 @@ if (defined $cgi->param('rememberedquery')) {
     my $list = join(" ", @collist);
     my $urlbase = Param("urlbase");
 
-    $cgi->send_cookie(-name => 'COLUMNLIST',
-                      -value => $list,
-                      -expires => 'Fri, 01-Jan-2038 00:00:00 GMT');
+    if ($list) {
+        $cgi->send_cookie(-name => 'COLUMNLIST',
+                          -value => $list,
+                          -expires => 'Fri, 01-Jan-2038 00:00:00 GMT');
+    }
+    else {
+        $cgi->remove_cookie('COLUMNLIST');
+    }
     if ($splitheader) {
         $cgi->send_cookie(-name => 'SPLITHEADER',
                           -value => $splitheader,