Fixing a third minor bug

When HTML output is not being created, the print functions last step is to call `html_out()`, which responds to `return` rather than `return 0`. This causes problems for lines of code that rely on receiving a return value of 0. For example:
```
[[ $VULN_COUNT -le $VULN_THRESHLD ]] && outln && pr_headlineln " Testing for LUCKY13 vulnerability " && outln
```

testssl.sh

@@ -569,7 +569,7 @@ html_reserved(){
 }
 
 html_out() {
-     "$do_html" || return
+     "$do_html" || return 0
      [[ -n "$HTMLFILE" ]] && [[ ! -d "$HTMLFILE" ]] && printf -- "%b" "${1//%/%%}" >> "$HTMLFILE"
      # here and other printf's: a little bit of sanitzing with bash internal search&replace -- otherwise printf will hiccup at '%'. '--' and %b do the rest.
 }