Use previous blog post index when deleting

src/freedombone-mesh-blog

         return
     fi
     CURRENT_INDEX=$(cat $CURRENT_BLOG_INDEX)
-    LAST_BLOG_ENTRY=$BLOG_CONTENT_PATH/${CURRENT_INDEX}_post.rst
+    PREVIOUS_INDEX=$((CURRENT_INDEX - 1))
+    LAST_BLOG_ENTRY=$BLOG_CONTENT_PATH/${PREVIOUS_INDEX}_post.rst
     if [ ! -f $LAST_BLOG_ENTRY ]; then
         return
     fi
     case $sel in
         0) rm $LAST_BLOG_ENTRY
            if [ $CURRENT_INDEX -gt 0 ]; then
-               CURRENT_INDEX=$((CURRENT_INDEX - 1))
+               CURRENT_INDEX=$PREVIOUS_INDEX
                echo "$CURRENT_INDEX" > $CURRENT_BLOG_INDEX
+           else
+               rm -f $CURRENT_BLOG_INDEX
            fi
            regenerate_blog
            ;;