Remove ctx->config.enc null check in encoder_init

Remove an unneeded null pointer check for ctx->config.enc in
encoder_init(). ctx->config.enc is set to a non-null pointer in
aom_codec_enc_init_ver().

Change-Id: Ibf72d190e4ce35f5c87e969a5ca09a58f5b78e7d
diff --git a/av1/av1_cx_iface.c b/av1/av1_cx_iface.c
index 6f0803e..a6102e6 100644
--- a/av1/av1_cx_iface.c
+++ b/av1/av1_cx_iface.c
@@ -1997,11 +1997,10 @@
     ctx->priv = (aom_codec_priv_t *)priv;
     ctx->priv->init_flags = ctx->init_flags;
 
-    if (ctx->config.enc) {
-      // Update the reference to the config structure to an internal copy.
-      priv->cfg = *ctx->config.enc;
-      ctx->config.enc = &priv->cfg;
-    }
+    // Update the reference to the config structure to an internal copy.
+    assert(ctx->config.enc);
+    priv->cfg = *ctx->config.enc;
+    ctx->config.enc = &priv->cfg;
 
     priv->extra_cfg = default_extra_cfg;
     aom_once(av1_initialize_enc);