SLING-8205 - Stop using Class.getField() in order to avoid throwing NoSuchFieldException

* iterate through Class.getFields; this can still throw an IllegalAccessException,
but less likely than the previous approach - closes #3
diff --git a/src/main/java/org/apache/sling/scripting/sightly/render/ObjectModel.java b/src/main/java/org/apache/sling/scripting/sightly/render/ObjectModel.java
index 6b437d7..e3ef0ad 100644
--- a/src/main/java/org/apache/sling/scripting/sightly/render/ObjectModel.java
+++ b/src/main/java/org/apache/sling/scripting/sightly/render/ObjectModel.java
@@ -367,12 +367,17 @@
         if (cls.isArray() && "length".equals(fieldName)) {
             return Array.getLength(object);
         }
-        try {
-            Field field = cls.getField(fieldName);
-            return field.get(object);
-        } catch (Exception e) {
-            return null;
+        for (Field field : cls.getFields()){
+            if (field.getName().equals(fieldName)){
+                try {
+                    return field.get(object);
+                }
+                catch (IllegalAccessException e) {
+                    return null;
+                }
+            }
         }
+        return null;
     }
 
     /**