cgen: fix match in map or expr (#10283)

vlib/v/gen/c/cgen.v

@@ -4037,7 +4037,8 @@ fn (mut g Gen) need_tmp_var_in_match(node ast.MatchExpr) bool {
 				if branch.stmts[0] is ast.ExprStmt {
 					stmt := branch.stmts[0] as ast.ExprStmt
 					if stmt.expr is ast.CallExpr || stmt.expr is ast.IfExpr
-						|| stmt.expr is ast.MatchExpr {
+						|| stmt.expr is ast.MatchExpr || (stmt.expr is ast.IndexExpr
+						&& (stmt.expr as ast.IndexExpr).or_expr.kind != .absent) {
 						return true
 					}
 				}

vlib/v/tests/match_in_map_or_expr_test .v

@@ -0,0 +1,15 @@
+fn test_match_in_map_or_expr() {
+	a := 5
+	some_map := map{
+		3: '3'
+		4: '4'
+	}
+	something := match a {
+		7 { '7' }
+		6 { '6' }
+		5 { '5' }
+		else { some_map[a] or { a.str() } } // here is the error
+	}
+	println(something)
+	assert something == '5'
+}