fix #197 - do not overwrite, if empty

src/main.ts

@@ -67,14 +67,14 @@ async function get_release_by_tag(
     updateObject.prerelease = false
   }
   if (overwrite) {
-    if (release.data.name !== release_name) {
+    if (release_name && release.data.name !== release_name) {
       core.debug(
         `The ${tag} release already exists with a different name ${release.data.name} so we'll overwrite it.`
       )
       updateObject = updateObject || {}
       updateObject.name = release_name
     }
-    if (release.data.body !== body) {
+    if (body && release.data.body !== body) {
       core.debug(
         `The ${tag} release already exists with a different body ${release.data.body} so we'll overwrite it.`
       )