fix: loading fails when plugin configuration is empty (#45)

Author: shuaijinchao

apisix/runner/http/request.py

@@ -333,7 +333,7 @@ def set_config(self, key: str, value: str):
         :param value:
         :return:
         """
-        if key and value:
+        if key:
             self.__configs[key] = value
             return True
         return False

tests/runner/http/test_request.py

@@ -107,7 +107,8 @@ def test_request_handler():
     assert req.set_headers({default_key: default_val})
     assert req.get_headers() == {default_key: default_val}
 
-    assert not req.set_config(default_key, default_empty_str)
+    assert not req.set_config(default_empty_str, default_empty_str)
+    assert req.set_config(default_key, default_empty_str)
     assert req.set_config(default_key, default_val)
     assert req.get_config(default_key) == default_val