Fixed missing register move in if statements

tests/programs/branch-save.q

@@ -0,0 +1,23 @@
+main() {
+	a, b := f(5)
+	assert a == 0
+	assert b == 5
+
+	a, b = f(15)
+	assert a == 1
+	assert b == 5
+
+	a, b = f(25)
+	assert a == 2
+	assert b == 5
+}
+
+f(b Int) -> (Int, Int) {
+	a := 0
+
+	if b >= 10 {
+		a, b = b / 10
+	}
+
+	return a, b
+}