draw-layer: Indent 'else' on the same level as 'if'

Fixes raised warnings from -Wmisleading-indentation

src/map/draw-layer.c

@@ -143,7 +143,7 @@ picplanner_draw_layer_size_allocate (GtkWidget  *widget,
         x_offset = 0;
         y_offset = (height-width)/2;
       }
-    else
+      else
       {
         min_size = height;
         x_offset = (width-height)/2;