Fixed handling of nested lambda expressions in sequence diagrams

tests/t20046/t20046.cc

@@ -0,0 +1,24 @@
+namespace clanguml {
+namespace t20046 {
+
+template <typename F> int a1(F &&f) { return f(42); }
+
+int a2(int x) { return 2; }
+
+int a3(int x) { return 3; }
+
+int tmain()
+{
+    // Call expression in a nested lambda
+    auto v1 = [](auto &&arg1) {
+        return [](auto &&arg2) { return a2(arg2); }(arg1);
+    }(0);
+
+    // Call expression in a nested lambda in call expression
+    auto v4 = a1(
+        [](auto &&arg1) { return [](auto &&arg2) { return a3(arg2); }(arg1); });
+
+    return 0;
+}
+}
+}