Fix: All cells are nulls if setter returns anything but void

Author: pbacz

src/main/java/io/github/millij/poi/util/Beans.java

@@ -68,7 +68,7 @@ public static String getFieldName(final Method method) {
      */
     public static String getFieldValueAsString(final Object beanObj, final String fieldName) throws Exception {
         // Property Descriptor
-        final PropertyDescriptor pd = new PropertyDescriptor(fieldName, beanObj.getClass());
+        final PropertyDescriptor pd = PROP_UTILS_BEAN.getPropertyDescriptor(beanObj, fieldName);
         final Method getterMtd = pd.getReadMethod();
 
         final Object value = getterMtd.invoke(beanObj);

src/test/java/io/github/millij/bean/Employee.java

@@ -67,8 +67,9 @@ public String getId() {
         return id;
     }
 
-    public void setId(String id) {
+    public Employee setId(String id) {
         this.id = id;
+        return this;
     }
 
     @SheetColumn("Name")