AVI: abort if user gave up while rebuilding the index (refs: #2872)

Previously, the core would fallback to other demux plugins which was
inefficient and error-prone.

modules/demux/avi/avi.c

@@ -765,7 +765,7 @@ error:
     }
     AVI_ChunkFreeRoot( p_demux->s, &p_sys->ck_root );
     free( p_sys );
-    return VLC_EGENERIC;
+    return vlc_object_alive( p_demux ) ? VLC_EGENERIC : VLC_ETIMEOUT;
 }
 
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