Tests: skip proxy cache conditional test if we didn't get etag.

spdy.t

diff --git a/spdy.t b/spdy.t
index 7847d41..b7932e0 100644
--- a/spdy.t
+++ b/spdy.t
@@ -243,16 +243,21 @@
 ($frame) = grep { $_->{type} eq "SYN_REPLY" } @$frames;
 is($frame->{headers}->{':status'}, '200 OK', 'proxy cache unconditional');
 
-my $ims = $frame->{headers}->{'etag'};
+my $etag = $frame->{headers}->{'etag'};
+
+SKIP: {
+skip 'no etag', 1 unless defined $etag;
 
 $sid2 = spdy_stream($sess, { path => '/proxy/t2.html',
-	headers => { "if-none-match" =>  $ims }
+	headers => { "if-none-match" =>  $etag }
 });
 $frames = spdy_read($sess, all => [{ sid => $sid2, fin => 1 }]);
 
 ($frame) = grep { $_->{type} eq "SYN_REPLY" } @$frames;
 is($frame->{headers}->{':status'}, 304, 'proxy cache conditional');
 
+}
+
 # request body (uses proxied response)
 
 $sess = new_session();