Adding gene not in the dataset brakes the app #48
Description
In the Gene Expression Heatmap panel of Wormcells-viz, heatmap keeps loading if we add (using paste list of Gene IDs option) a gene that might not be available in the data. (Gene to reproduce the scenario: WBGene00044083). It could be confusing for the users. Hence, an error or warning message is required for such scenarios.