fix to make sure axis layout defaults are used when no image present

Author: antoinerg

src/plots/cartesian/layout_defaults.js

@@ -302,12 +302,12 @@ module.exports = function supplyLayoutDefaults(layoutIn, layoutOut, fullData) {
         axLayoutIn = layoutIn[axName];
         axLayoutOut = layoutOut[axName];
 
-        var scaleanchorDflt = null;
+        var scaleanchorDflt;
         if(axLetter === 'y' && !axLayoutIn.hasOwnProperty('scaleanchor') && axHasImage[axName]) {
             scaleanchorDflt = axLayoutOut.anchor;
         }
 
-        var constrainDflt = null;
+        var constrainDflt;
         if(!axLayoutIn.hasOwnProperty('constrain') && axHasImage[axName]) {
             constrainDflt = 'domain';
         }

test/jasmine/tests/image_test.js

@@ -172,8 +172,8 @@ describe('image smart layout defaults', function() {
         gd.data = [{type: 'image', z: [[[255, 0, 0]]]}];
         gd.layout = {yaxis: {constrain: false}, xaxis: {constrain: false}};
         supplyAllDefaults(gd);
-        expect(gd._fullLayout.xaxis.constrain).toBe(undefined);
-        expect(gd._fullLayout.yaxis.constrain).toBe(undefined);
+        expect(gd._fullLayout.xaxis.constrain).toBe('range');
+        expect(gd._fullLayout.yaxis.constrain).toBe('range');
     });
 });