Fix wrong error with immutables when base contract c'tor uses return

test/libsolidity/syntaxTests/immutable/base_ctor_return_no_immutables.sol

@@ -0,0 +1,10 @@
+contract Parent {
+    constructor() {
+        return;
+    }
+}
+
+contract Child is Parent {
+    uint public immutable baked = 123;
+}
+