Fix build when vp8 is disabled

Change-Id: Ie1765f086b10d0f7c4d72961d238dfe0d6056dc2
diff --git a/test/encode_test_driver.cc b/test/encode_test_driver.cc
index f3c3243..f4c4c4b 100644
--- a/test/encode_test_driver.cc
+++ b/test/encode_test_driver.cc
@@ -56,10 +56,12 @@
 #endif  // !CONFIG_EXT_TILE
     } else
 #endif
-    if (CodecInterface() == &vpx_codec_vp8_cx_algo) {
+    {
 #if CONFIG_VP8_ENCODER
-      ASSERT_EQ(&vpx_codec_vp8_cx_algo, CodecInterface())
-          << "Unknown Codec Interface";
+      if (CodecInterface() == &vpx_codec_vp8_cx_algo) {
+        ASSERT_EQ(&vpx_codec_vp8_cx_algo, CodecInterface())
+            << "Unknown Codec Interface";
+      }
 #endif
     }
   }