fix(core): gracefully handle missing Exif.Composite.ImageSize

Fixes #226

src/model/metadata.js

@@ -133,7 +133,7 @@ function makeArray (value) {
 
 function dimensions (exif) {
   // Use the Composite field to avoid having to check all possible tag groups (EXIF, QuickTime, ASF...)
-  if (!exif.Composite) {
+  if (!exif.Composite || !exif.Composite.ImageSize) {
     return {
       width: null,
       height: null

test/model/metadata.spec.js

@@ -228,11 +228,19 @@ describe('Metadata', function () {
       should(meta.height).eql(600)
     })
 
-    it('defaults to null otherwise', function () {
+    it('defaults to null when there is no Composite data', function () {
       const exiftool = fixtures.exiftool()
       const meta = new Metadata(exiftool)
       should(meta.width).eql(null)
       should(meta.width).eql(null)
     })
+
+    it('defaults to null when there is no ImageSize data', function () {
+      const exiftool = fixtures.exiftool()
+      exiftool.Composite = { Other: 'Data' }
+      const meta = new Metadata(exiftool)
+      should(meta.width).eql(null)
+      should(meta.width).eql(null)
+    })
   })
 })