According to the MissingMethodException error message, the data type of “variable” in your statement (below) is a String rather than an Integer.
WebUI.dragAndDropByOffset(findTestObject('slider/slider_meninggal'), variable, 0)
Perhaps change your statement to:
WebUI.dragAndDropByOffset(findTestObject('slider/slider_meninggal'), Integer.parseInt(variable), 0)