Refuse to upload empty files

Signed-off-by: fbt <fbt@fleshless.org>

ufw

@@ -442,7 +442,15 @@ main() {
 			(( ${#args[@]} )) || return 1
 
 			for t in "${args[@]}"; do
-				upload "$t"
+				if [[ -s "$t" ]]; then
+					upload "$t"
+				else
+					if [[ -f "$t" ]]; then
+						err "$t is empty"
+					else
+						err "$t not found"
+					fi
+				fi
 			done
 		;;