Ensure a response to "Nearby Markers" even if there are none

This is a longstanding easy to fix bug. We now report "No nearby markers"
rather than stay silent.

Author: davecraig

app/src/main/java/org/scottishtecharmy/soundscape/geoengine/GeoEngine.kt

@@ -848,8 +848,16 @@ class GeoEngine {
         val gridFinishTime = timeSource.markNow()
         Log.e(GridState.TAG, "Time to calculate NearbyMarkers: ${gridFinishTime - gridStartTime}")
 
-        if(results.isEmpty())
-            return null
+        if(results.isEmpty()) {
+            results.add(
+                PositionedString(
+                    text = localizedContext.getString(R.string.callouts_no_nearby_markers),
+                    type = AudioType.STANDARD,
+                    earcon = NativeAudioEngine.EARCON_MODE_EXIT
+                )
+            )
+        }
+
 
         return TrackedCallout(
             userGeometry = userGeometry,

app/src/main/res/values/strings.xml

@@ -304,6 +304,8 @@
 <string name="callouts_nothing_to_call_out_now">"There is nothing to call out right now"</string>
 <!-- Button text for the hear my surroundings button which calls out nearby markers -->
 <string name="callouts_nearby_markers">"Nearby Markers"</string>
+<!-- Text read out when there are no markers nearby to report -->
+<string name="callouts_no_nearby_markers">"There are no nearby markers"</string>
 <!-- Sleep Title, Sleep. Putting the app in an idle state for a period of time. -->
 <string name="sleep_sleep">"Sleep"</string>
 <!-- App is currently Sleeping. Putting the app in an idle state for a period of time. -->