cgen: fix struct init with multiple branches, fixes #11564 (#11570)

vlib/v/gen/c/cgen.v

@@ -4798,6 +4798,7 @@ fn (mut g Gen) if_expr(node ast.IfExpr) {
 		}
 	}
 	g.writeln('}')
+	g.stmt_path_pos << g.out.len
 	if needs_tmp_var {
 		if g.infix_left_var_name.len > 0 {
 			g.indent--

vlib/v/tests/init_multiple_branches_test.v

@@ -0,0 +1,34 @@
+// fixes https://github.com/vlang/v/issues/11564, test is copied from the code by https://github.com/ken0x0a and formatted
+import x.json2
+
+struct SA {}
+
+struct SB {}
+
+struct SC {}
+
+type Sum = SA | SB | SC
+
+struct App {
+	s map[string]Sum
+	t bool
+}
+
+fn test_init_multiple_branches() ? {
+	mut m := map[string]json2.Any{}
+	app := App{
+		t: m['t'] or { 0 }.bool()
+		s: if a := m['a'] {
+			println('a => $a')
+			b := return_optional(a) ? // Fails only if the expr in this line has or_block (or_block kind (.propagation or .block) doesn't matter)
+			b
+		} else {
+			map[string]Sum{}
+		}
+	}
+	println('app => $app')
+}
+
+fn return_optional(input json2.Any) ?map[string]Sum {
+	return map[string]Sum{}
+}