Merge pull request #1019 from sjinks/issue-1018

[BUG] Phalcon\Element::addFilter() prepends inserts NULL as the first element

Author: Phalcon

ext/forms/element.c

@@ -188,8 +188,11 @@ PHP_METHOD(Phalcon_Forms_Element, addFilter){
 	} else {
 		PHALCON_INIT_VAR(new_filters);
 		array_init_size(new_filters, 2);
-		phalcon_array_append(&new_filters, filters, PH_SEPARATE);
-		phalcon_array_append(&new_filters, filter, PH_SEPARATE);
+		if (Z_TYPE_P(filters) == IS_STRING) {
+			phalcon_array_append(&new_filters, filters, 0);
+		}
+
+		phalcon_array_append(&new_filters, filter, 0);
 		phalcon_update_property_this(this_ptr, SL("_filters"), new_filters TSRMLS_CC);
 	}