Do not make unsupported codec a php fatal error.

PHP Fatal error:  Could not find decoder for movie.flv in ffmpeg-info.php on line 15

Signed-off-by: Elan Ruusamäe <glen@delfi.ee>
--- ffmpeg-php-0.6.0/ffmpeg_movie.c~	2008-10-14 01:46:53.000000000 +0300
+++ ffmpeg-php-0.6.0/ffmpeg_movie.c	2010-08-24 15:37:30.402235881 +0300
@@ -501,7 +501,7 @@
                     codec_id));
 
         if (!decoder) {
-            zend_error(E_ERROR, "Could not find decoder for %s", 
+            zend_error(E_WARNING, "Could not find decoder for %s", 
                     _php_get_filename(ffmovie_ctx));
             return NULL;
         }