libavformat: Make protocols pass URLContext as log context where available

Since the libavformat major bump, URLContext contains an AVClass,
making it a usable log context.

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/gopher.c

@@ -50,7 +50,7 @@ static int gopher_connect(URLContext *h, const char *path)
             if (!path) return AVERROR(EINVAL);
             break;
         default:
-            av_log(NULL, AV_LOG_WARNING,
+            av_log(h, AV_LOG_WARNING,
                    "Gopher protocol type '%c' not supported yet!\n",
                    *path);
             return AVERROR(EINVAL);