mkm3u: Allow clearing the prevailing expected duration.

diff --git a/mkm3u b/mkm3u
index 5226697..1512e86 100755 (executable)
--- a/mkm3u
+++ b/mkm3u
@@ -572,9 +572,12 @@ class EpisodeListParser (object):
 
     elif cmd == "explen":
       w = ww.rest(); check(w is not None, "missing duration spec")
-      d, v = parse_duration(w)
-      me._explen = d
-      if v is not None: me._expvar = v
+      if w == "-":
+        me._explen, me._expvar = None, DEFAULT_EXPVAR
+      else:
+        d, v = parse_duration(w)
+        me._explen = d
+        if v is not None: me._expvar = v
 
     elif cmd == "epname":
       for k, v in me._keyvals(opts): me._bad_keyval("epname", k, v)