[BUGFIX] add missing variables for advanced 4 column grid (#462)

Author: mesosa

Resources/Private/Templates/GridElements/Adv4ColumnGrid.html

@@ -22,6 +22,13 @@
 	<f:variable name="column_3_offset">{data.pi_flexform.data.columns.lDEF.column_3_offset.vDEF}</f:variable>
 	<f:variable name="column_3_class">{data.pi_flexform.data.columns.lDEF.column_3_class.vDEF}</f:variable>
 
+	<f:variable name="column_4_xs">{data.pi_flexform.data.columns.lDEF.column_4_xs.vDEF}</f:variable>
+	<f:variable name="column_4_sm">{data.pi_flexform.data.columns.lDEF.column_4_sm.vDEF}</f:variable>
+	<f:variable name="column_4_md">{data.pi_flexform.data.columns.lDEF.column_4_md.vDEF}</f:variable>
+	<f:variable name="column_4_lg">{data.pi_flexform.data.columns.lDEF.column_4_lg.vDEF}</f:variable>
+	<f:variable name="column_4_offset">{data.pi_flexform.data.columns.lDEF.column_4_offset.vDEF}</f:variable>
+	<f:variable name="column_4_class">{data.pi_flexform.data.columns.lDEF.column_4_class.vDEF}</f:variable>
+
 	<f:comment><!-- ### Content ### --></f:comment>
 	<div class="row">
 			<div class="col1 {column_1_xs} {column_1_sm} {column_1_md} {column_1_lg} {column_1_offset} {column_1_class} ">