Add if statement around content printing

Some list pages, such as tags and categories, don't have content. Added
an if statement around the content panel to avoid displaying an empty
panel.

layouts/_default/list.html

@@ -1,7 +1,9 @@
 {{ define "main" }}
+	{{- if gt (len .Content) 0 }}
 	<div class="panel space-y-2">
 		{{ .Content }}
 	</div>
+	{{- end }}
 	{{ range .Pages.ByPublishDate.Reverse }}
 	{{- $images := default (slice "/imgs/no-image-new.webp" "/imgs/no-image-new.png") .Params.Images }}
 	{{- $altText := default "No alt text" .Params.ImageAltText }}