Merge branch 'develop' into feature/android-capacitator

src/Logic/FeatureSource/Sources/FilteringFeatureSource.ts

@@ -30,6 +30,9 @@ export default class FilteringFeatureSource implements FeatureSource {
         upstream.features.addCallback(() => {
             self.update()
         })
+        layer.isDisplayed.addCallback(() => {
+            self.update()
+        })
 
         layer.appliedFilters.forEach((value) =>
             value.addCallback((_) => {

src/Logic/Tags/Tag.ts

@@ -170,8 +170,12 @@ export class Tag extends TagsFilter {
         return <any>this
     }
 
+    /**
+     * new Tag("panoramax", "").isNegative() // => true
+     * new Tag("x","y").isNegative() // => false
+     */
     isNegative(): boolean {
-        return false
+        return this.value === ""
     }
 
     visit(f: (tagsFilter: TagsFilter) => void) {