plugs filter: return empty list if none chosen (#9)

app/src/main/java/net/vonforst/evmap/adapter/DataBindingAdapters.kt

@@ -223,7 +223,6 @@ class FiltersAdapter : DataBindingAdapter<FilterWithValue<FilterValue>>() {
                     value.values.add(choice.key)
                 } else {
                     value.values.remove(choice.key)
-                    value.all = false
                 }
                 updateButtons()
             }

app/src/main/java/net/vonforst/evmap/viewmodel/MapViewModel.kt

@@ -149,6 +149,10 @@ class MapViewModel(application: Application, geApiKey: String) : AndroidViewMode
         val connectorsVal =
             filters.find { it.value.key == "connectors" }!!.value as MultipleChoiceFilterValue
         val connectors = if (connectorsVal.all) null else connectorsVal.values.joinToString(",")
+        if (connectorsVal.values.isEmpty() && !connectorsVal.all) {
+            // no connectors chosen
+            return Resource.success(emptyList())
+        }
 
         // do not use clustering if filters need to be applied locally.
         val useClustering = minConnectors <= 1