check if the paste contents is empty

src/main/resources/templates/index.html

@@ -47,6 +47,10 @@
         var pasteInput = document.getElementById('paste-input');
         var paste = pasteInput.value;
 
+        if (!paste || paste.trim() === ''){
+            return;
+        }
+
         fetch('/api/upload', {
             method: 'POST',
             headers: {