fix JSONPath npe

src/main/java/com/alibaba/fastjson/JSONPath.java

@@ -3848,6 +3848,9 @@ protected Object getPropertyValue(Object currentObject, String propertyName, lon
         if (currentObject instanceof String) {
             try {
                 JSONObject object = (JSONObject) JSON.parse((String) currentObject, parserConfig);
+                if (object == null) {
+                    return null;
+                }
                 currentObject = object;
             } catch (Exception ex) {
                 // skip

src/test/java/com/alibaba/fastjson/jsonpath/issue4385/TestIssue4385.java

@@ -0,0 +1,21 @@
+package com.alibaba.fastjson.jsonpath.issue4385;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import com.alibaba.fastjson.JSONObject;
+import com.alibaba.fastjson.JSONPath;
+
+/**
+ * @author vdisk
+ */
+public class TestIssue4385 {
+
+    @Test
+    public void testIssue4385() {
+        JSONObject jsonObject = new JSONObject();
+        jsonObject.put("key1", "");
+        Object value = JSONPath.eval(jsonObject, "$.key1.key2");
+        Assert.assertNull(value);
+    }
+}