Fix Highcharts column chart not rendering second series when first series is all zeros (#964)

* Initial plan

* Fix column chart not displaying second series when first series has all-zero values

Co-authored-by: Redjaw <4438516+Redjaw@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Redjaw <4438516+Redjaw@users.noreply.github.com>

Author: 2 people

knowagecockpitengine/src/main/resources/chart/templates/highcharts/column_chart.vm

@@ -1550,8 +1550,8 @@
 	    	    #set($serieColumnsMapped = $dataColumnsMapper.get($relatedSerieColName.toLowerCase())) ## "Vendite_AVG" -> "column_5" ## "Ricavi_sum" -> "column_6"
 
 	    		#foreach($row in $rows)
-					#if( $row.get($serieColumnsMapped))
-						#set ($serieValue = $row.get($serieColumnsMapped))
+					#set ($serieValue = $row.get($serieColumnsMapped))
+					#if("$!serieValue" != "")
 						#set ($serieCategoryName =  $row.get($categorieColumnsMapped))
 
 						#set( $serieCategoryName = $escapeTool.javascript($serieCategoryName))