cli: Check parser output before transforming AST

alib2cli/src/parser/Parser2.cpp

@@ -38,12 +38,17 @@ std::unique_ptr<CommandList> Parser2::parse(antlr4::CharStream& stream)
     parser.setErrorHandler(std::make_shared<antlr4::DefaultErrorStrategy>());
     AltCliParser::ParseContext* tree = parser.parse();
-    auto command = AltVisitor().transform(tree);
-
     if (listener->any()) {
         throw exception::CommonException(listener->getErrors());
     }
+    if (tree == nullptr) {
+        throw exception::CommonException("Invalid parse");
+    }
+
+    auto command = AltVisitor().transform(tree);
+
+
     return command;
 }
 } // cli