Clone the geometry before applying the decimals transform

We may only do it if the geometry has not been previously transformed.

src/ol/format/feature.js

@@ -206,6 +206,9 @@ ol.format.Feature.transformWithOptions = function(
     if (Array.isArray(transformed)) {
       transform(transformed);
     } else {
+      if (transformed === geometry) {
+        transformed = transformed.clone();
+      }
       transformed.applyTransform(transform);
     }
   }

test/spec/ol/format/geojson.test.js

@@ -826,6 +826,8 @@ describe('ol.format.GeoJSON', function() {
       });
       expect(format.readGeometry(geojson).getCoordinates()).to.eql(
           [[42.123457, 38.987654], [43, 39]]);
+      expect(linestring.getCoordinates()).to.eql(
+          [[42.123456789, 38.987654321], [43, 39]]);
     });
   });