Avoid exceptions parsing playlist writer configuration.

These may have been caused by overzealous avoidance of reflection.

src/beat_link_trigger/playlist_writer.clj

@@ -301,7 +301,7 @@
   "Retrieve the preferred minimum time, in seconds, a track must be
   playing in order to get written to the playlist."
   []
-  (or (when-let [^String pref (min-time-pref-key (prefs/get-preferences))]
+  (or (when-let [pref (min-time-pref-key (prefs/get-preferences))]
         (try
           (Long/valueOf pref)
           (catch Exception e
@@ -312,7 +312,7 @@
   "Retrieve the preference setting for filtering out players that are
   not On-Air."
   []
-  (or (when-let [^String pref (on-air-pref-key (prefs/get-preferences))]
+  (or (when-let [pref (on-air-pref-key (prefs/get-preferences))]
         (try
           (Boolean/valueOf pref)
           (catch Exception e
@@ -324,7 +324,7 @@
   playlist file when all players have been stopped for a threshold
   interval."
   []
-  (or (when-let [^String pref (split-pref-key (prefs/get-preferences))]
+  (or (when-let [pref (split-pref-key (prefs/get-preferences))]
         (try
           (Boolean/valueOf pref)
           (catch Exception e
@@ -336,7 +336,7 @@
   before forcing the start of a new playlist when a new track starts
   playing."
   []
-  (or (when-let [^String pref (new-playlist-threshold-pref-key (prefs/get-preferences))]
+  (or (when-let [pref (new-playlist-threshold-pref-key (prefs/get-preferences))]
         (try
           (Long/valueOf pref)
           (catch Exception e