[gnome-maps/gnome-3-36] layersPopover: Fix crash when no aerial tiles defined

[Marcus Lundblad <mlundblad src gnome org>]

commit 22e32384f5d3623d8fdc8c330a0adcda3047cd7a
Author: Marcus Lundblad <ml update uu se>
Date:   Thu Jun 3 23:22:56 2021 +0200

    layersPopover: Fix crash when no aerial tiles defined
    
    Fixes a crash when no aerial tiles is defined.

 src/layersPopover.js | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)
---
diff --git a/src/layersPopover.js b/src/layersPopover.js
index 45664823..74e37abc 100644
--- a/src/layersPopover.js
+++ b/src/layersPopover.js
@@ -97,13 +97,16 @@ var LayersPopover = GObject.registerClass({
                 source: MapSource.createStreetSource(),
                 widget: this._streetLayerImage,
                 lastLocation: { x: -1, y: -1, z: -1 }
-            },
-            aerial: {
+            }
+        };
+
+        if (Service.getService().tiles.aerial) {
+            this._layerPreviews.aerial = {
                 source: MapSource.createAerialSource(),
                 widget: this._aerialLayerImage,
                 lastLocation: { x: -1, y: -1, z: -1 }
-            }
-        };
+            };
+        }
 
         // disable the map type switch buttons if aerial is unavailable
         if (Service.getService().tiles.aerial) {