fix ios line gradient crash and LineChart popup IOOBE#168

NadeemIqbal wants to merge 2 commits into

ehsannarmani:masterehsannarmani/ComposeCharts:masterfrom

NadeemIqbal:fix/ios-shader-and-empty-data-guardsNadeemIqbal/ComposeCharts:fix/ios-shader-and-empty-data-guardsCopy head branch name to clipboard