don't show empty tooltips in backgrounds list

modules/renderer/background_source.js

@@ -79,6 +79,13 @@ export function rendererBackgroundSource(data) {
     };
 
 
+    source.hasDescription = function() {
+        var id_safe = source.id.replace(/\./g, '<TX_DOT>');
+        var descriptionText = localizer.tInfo('imagery.' + id_safe + '.description', { default: escape(_description) }).text;
+        return descriptionText !== '';
+    };
+
+
     source.description = function() {
         var id_safe = source.id.replace(/\./g, '<TX_DOT>');
         return t.append('imagery.' + id_safe + '.description', { default: escape(_description) });

modules/ui/sections/background_list.js

@@ -142,7 +142,7 @@ export function uiSectionBackgroundList(context) {
             var item = d3_select(this).select('label');
             var span = item.select('span');
             var placement = (i < nodes.length / 2) ? 'bottom' : 'top';
-            var description = d.description();
+            var hasDescription = d.hasDescription();
             var isOverflowing = (span.property('clientWidth') !== span.property('scrollWidth'));
 
             item.call(uiTooltip().destroyAny);
@@ -153,10 +153,10 @@ export function uiSectionBackgroundList(context) {
                     .title(() => t.append('background.switch'))
                     .keys([uiCmd('⌘' + t('background.key'))])
                 );
-            } else if (description || isOverflowing) {
+            } else if (hasDescription || isOverflowing) {
                 item.call(uiTooltip()
                     .placement(placement)
-                    .title(() => description || d.label())
+                    .title(() => hasDescription ? d.description() : d.label())
                 );
             }
         });