Do not render Items heading when not present

templates/invoice.tex

@@ -171,11 +171,12 @@ SWIFT/BIC: & \multicolumn{1}{l|}{ {{issuer.swift}} } & \multicolumn{2}{l}{\Deliv
 &&& \\
 
 % ITEM(s) HEADING
+{{if invoice.itemheading}}
 {{for heading in invoice.itemheading}}
 \multicolumn{4}{l}{ {{heading}} } \\
 {{endfor}}
-
 &&& \\
+{{endif}}
 
 % ITEMS
 \multicolumn{4}{X}{%