Fix handling unexpected loggernet output

scripts/loggernet_rotate.sh

@@ -52,7 +52,7 @@ EOF
 # specially handles 2400 which should go for the next day, not the past day
 yyyy_jjj_tower_split() {
     awk_command='
-NR>header_size {
+(NR>header_size) && ($1 == "1") {
 time_spec = sprintf("%04d 01 %03d 00 00 00", $2, $3);
 epoch_seconds = mktime(time_spec);
 if ($4 == "2400")
@@ -110,7 +110,12 @@ for file_suffix in $FILE_SUFFIXES; do
     yyyy_jjj_tower_split $input_file
 
     # copy the header back to the original file
-    cp $header_fn $input_file
+    if [ -s $header_fn ]; then
+        cp $header_fn $input_file
+    else
+        # loggernet doesn't like empty destination files
+        rm $input_file
+    fi
 
     # remove the temporary header file
     rm ${header_fn}