src/talks.sh: Do not output watch link text if missing video-url

This is the case right now with cs4m, since I just gave the talk
and the video will not likely be available for a couple of weeks.

src/talks.sh

@@ -41,7 +41,11 @@ talk-field()
   local -r id=${1?Missing talk id}
   local -r field=${2?Missing talk field}
 
-  recsel -P "$field" -e "id = '$id'" "$TALKFILE"
+  local result status
+  result=$( recsel -P "$field" -e "id = '$id'" "$TALKFILE" )
+  status=$?
+
+  [ $? -a -n "$result" ] && echo "$result"
 }
 
 
@@ -56,18 +60,23 @@ abstract()
   locimg=$( talk-field "$id" locimg )
   date=$( talk-field "$id" date )
   abstract=$( talk-field "$id" abstract )
-  url=$( talk-field "$id" video-url )
+  url=$( talk-field "$id" video-url || echo "#$id" )
   links=$( talk-field "$id" link )
 
   local abstract_html
   abstract_html=$( pandoc -fmarkdown -thtml5 <<< "$abstract" )
 
+  local watch_title=
+  if [[ ! "$url" =~ ^# ]]; then
+    watch_title="Watch $location Talk"
+  fi
+
   cat <<EOF
 <article class="abstract talk">
   <h2 class="title" id="$id">$title</h2>
 
   <ul class="links">
-    <li><a class="video $locimg" href="$url">Watch $location Talk</a></li>
+    <li><a class="video $locimg" href="$url">$watch_title</a></li>
     $(
       while read lurl ltitle; do
         printf "<li><a href="%s">%s</a></li>\n" "$lurl" "$ltitle"