do not send an email when the body is empty

PKGBUILD

@@ -1,7 +1,7 @@
 # Maintainer: Yves G. <theYinYeti@yalis.fr>
 
 pkgname=epsi2ical
-pkgver=0.1
+pkgver=0.3
 pkgrel=1
 pkgdesc="Create an ICS file based on EPSI’s web calendar"
 arch=('any')

epsiEDTtoICS.sh

@@ -103,11 +103,7 @@ function unwrap_ical_long_lines() {
 # $1: path to the old file
 # $2: path to the new file
 function format_diff_and_send_mail() {
-  {
-    echo "To: $TO"
-    echo "Subject: Changes in EPSI calendar"
-    echo
-    diff -u8 \
+  icalChanges="$(diff -u8 \
       <(crlf_to_lf <"$1" | unwrap_ical_long_lines | grep -vE '^DTSTAMP:|^UID:') \
       <(crlf_to_lf <"$2" | unwrap_ical_long_lines | grep -vE '^DTSTAMP:|^UID:') \
     | awk '
@@ -119,23 +115,30 @@ function format_diff_and_send_mail() {
       /BEGIN:VEVENT/  { inEvent=1; diff="\n"; next }
       $0 ~ /^[-+]/    { inDiff=1 }
       /^@|END:VEVENT/ { out() }
-                      { diff=diff $0 "\n" }' \
-    | while IFS='' read -r l; do
-      case "$l" in
-      '')
-        echo; continue ;;
-      ?DT*)
-        h="$(sed -r 's/^.DT(.*):.*/\1/' <<<"$l")"
-        v="$(date -d $(sed -r 's/.*:(....)(..)(..T..)(..)(..Z)/\1-\2-\3:\4:\5/' <<<"$l"))" ;;
-      *)
-        IFS=: read -r h v <<<"${l#?}" ;;
-      esac
-      printf '%s %11s: %s\n' "${l:0:1}" "$h" "$v"
-    done
-  } \
-  | lf_to_crlf \
-  | sendmail -t 2>&1 \
-  | log 3 -
+                      { diff=diff $0 "\n" }')"
+  if [ -n "$icalChanges" ]; then
+    {
+      echo "To: $TO"
+      echo 'Subject: Changes in EPSI calendar'
+      echo 'Content-Type: text/plain; charset=UTF-8'
+      echo
+      while IFS='' read -r l; do
+        case "$l" in
+        '')
+          echo; continue ;;
+        ?DT*)
+          h="$(sed -r 's/^.DT(.*):.*/\1/' <<<"$l")"
+          v="$(date -d $(sed -r 's/.*:(....)(..)(..T..)(..)(..Z)/\1-\2-\3:\4:\5/' <<<"$l"))" ;;
+        *)
+          IFS=: read -r h v <<<"${l#?}" ;;
+        esac
+        printf '%s %11s: %s\n' "${l:0:1}" "$h" "$v"
+      done <<<"$icalChanges"
+    } \
+    | lf_to_crlf \
+    | sendmail -t 2>&1 \
+    | log 3 -
+  fi
 }
 
 function write_output_and_send_mail() {