Fix #template 0 causing an error (#751)

Thanks @kidglove57 for spotting this issue and helping me track down the
cause!

---------

Co-authored-by: Matiss Janis Aboltins <matiss@mja.lv>

packages/loot-core/src/server/budget/goaltemplates.js

@@ -226,7 +226,7 @@ async function applyCategoryTemplate(category, template_lines, month, force) {
             limit = amountToInteger(template.limit);
           }
         }
-        if (template.monthly) {
+        if (template.monthly != null) {
           let monthly = amountToInteger(template.monthly);
           to_budget += monthly;
         } else {

upcoming-release-notes/751.md

+---
+category: Bugfix
+authors: [j-f1]
+---
+
+Fix `#template 0` causing an error