Add support for unless

ifs without a true branch would crash before
Somewhat more verbose but unified

test/mom/test_if_no_else.rb

@@ -24,7 +24,6 @@ module Risc
       produced = produce_body
       check = produced.next(4)
       assert_equal IsZero , check.class
-      assert check.label.name.start_with?("merge_label") , check.label.name
     end
     def test_false_label
       produced = produce_body

test/mom/test_if_no_if.rb

@@ -0,0 +1,56 @@
+require_relative "helper"
+
+module Risc
+  class TestIfNoIf < MiniTest::Test
+    include Statements
+
+    def setup
+      super
+      @input = "unless(@a) ; arg = 5 ; end"
+      @expect = [SlotToReg, SlotToReg, LoadConstant, OperatorInstruction, IsZero, #4
+                 LoadConstant, OperatorInstruction, IsZero, Label, Branch, #9
+                 Label, LoadConstant, SlotToReg, RegToSlot, Label] #14
+   end
+
+    def test_if_instructions
+      assert_nil msg = check_nil , msg
+    end
+
+    def test_false_load
+      produced = produce_body
+      assert_equal Parfait::FalseClass , produced.next(2).constant.class
+    end
+    def test_isnotzero
+      produced = produce_body
+      check = produced.next(4)
+      assert_equal IsZero , check.class
+      assert check.label.name.start_with?("false_") , check.label.name
+    end
+    def test_false_label
+      produced = produce_body
+      assert_equal Label , produced.next(10).class
+    end
+    def test_false_check
+      produced = produce_body
+      assert_equal produced.next(10).name , produced.next(4).label.name
+    end
+    def test_nil_load
+      produced = produce_body
+      assert_equal Parfait::NilClass , produced.next(5).constant.class
+    end
+    def est_nil_check
+      produced = produce_body
+      assert_equal Label , produced.next(4).label.class
+      assert_equal produced.next(12) , produced.next(4).label
+    end
+    def test_true_label
+      produced = produce_body
+      assert produced.next(8).name.start_with?("true_label")
+    end
+    def test_merge_label
+      produced = produce_body
+      assert produced.next(14).name.start_with?("merge_label")
+    end
+
+  end
+end