add empty check for avatar url

entrypoint.sh

@@ -122,15 +122,15 @@ if [ "${INPUT_AVATARS_AUTO_FETCH}" == "true" ]; then
     # Use github api to get avatar url using the author name or email
     avatar_by_name=$(wget -O - -o /dev/null https://api.github.com/users/$name | jq -r '.avatar_url')
 
-    if [ "$avatar_by_name" != "null" ]; then
+    if ([ "$avatar_by_name" != "null" ] && [ ! -z "$avatar_by_name" ]); then
       printf "\n> \t\tDownloading avatar for $name from: $avatar_by_name"
       wget -O "/gource/avatars/$name.png" $avatar_by_name >/dev/null 2>&1
       ((avatarsCount=avatarsCount+1))
       continue
     fi
 
     avatar_by_email=$(wget -O - -o /dev/null https://api.github.com/search/users?q=$email | jq -r '.items[0].avatar_url')
-    if [ "$avatar_by_email" != "null" ]; then
+    if ([ "$avatar_by_email" != "null" ] && [ ! -z "$avatar_by_name" ]); then
       printf "\n> \t\tDownloading avatar for $email from: $avatar_by_email"
       wget -O "/gource/avatars/$name.png" $avatar_by_email >/dev/null 2>&1
       ((avatarsCount=avatarsCount+1))