Fix install failing if test domain used but no TEST_REQUIREMENTS defined.

Author: rnixx

CHANGES.md

@@ -2,6 +2,8 @@
 
 ## 1.1.0 (unreleased)
 
+- Fix install failing if test domain used but no `TEST_REQUIREMENTS` defined.
+
 - Feature: Add target `zope-adduser` to create an emergency user.
 
 ## 1.0 (2025-02-11)

src/mxmake/topics/qa/test.mk

@@ -28,7 +28,7 @@
 TEST_TARGET:=$(SENTINEL_FOLDER)/test.sentinel
 $(TEST_TARGET): $(MXENV_TARGET)
 	@echo "Install $(TEST_REQUIREMENTS)"
-	@$(PYTHON_PACKAGE_COMMAND) install $(TEST_REQUIREMENTS)
+	@test -z "$(TEST_REQUIREMENTS)" || $(PYTHON_PACKAGE_COMMAND) install $(TEST_REQUIREMENTS)
 	@touch $(TEST_TARGET)
 
 .PHONY: test