Dubbo 2.7.6 breaks the generic invocation behavior

[JasonMing]

Environment

• Dubbo version: 2.7.6 +

Steps to reproduce this issue

GenericService genericService = ...;
genericService.$invoke("method", null /* parameterTypes */, new Object[] { /* args */ });

Before 2.7.6, the parameterType parameter supports null value, means use the method without overloads.

However, since 2.7.6, see: ad2d30b#diff-d799d91b73870eef3c22b89216a3554fR74, a check args.length != types.length was added. An NPE will be thrown when types is null.

Expected Result

Support nullable parameterTypes.

Actual Result

A guard check args.length != types.length in ad2d30b#diff-d799d91b73870eef3c22b89216a3554fR74 causes NPE when types is null.

[JasonMing]

@sunchuanleihit could you please check this issue?

[manzhizhen]

Let me have a look