Fix negative number of trips in ImproveOSM issues

See https://github.com/openstreetmap/iD/pull/5739#issuecomment-460786055

data/core.yaml

@@ -684,6 +684,7 @@ en:
         mr:
           title: Missing Geometry
           description: '{num_trips} recorded trips in this area suggest there may be unmapped {geometry_type} here.'
+          description_alt: 'Data from a 3rd party suggests there may be unmapped {geometry_type} here.'
         tr:
           title: Missing Turn Restriction
           description: '{num_passed} of {num_trips} recorded trips (travelling {travel_direction}) make a turn from {from_way} to {to_way} at {junction}. There may be a missing "{turn_restriction}" restriction.'
@@ -1547,4 +1548,4 @@ en:
   wikidata:
     identifier: "Identifier"
     label: "Label"
-    description: "Description"
+    description: "Description"