Upon select all in upload files activity, enable upload button

Signed-off-by: tobiasKaminsky <tobias@kaminsky.me>

src/main/java/com/owncloud/android/ui/activity/UploadFilesActivity.java

@@ -418,6 +418,8 @@ public class UploadFilesActivity extends DrawerActivity implements LocalFileList
             selectAll.setIcon(
                 ThemeDrawableUtils.tintDrawable(R.drawable.ic_select_all, ThemeColorUtils.primaryColor(this)));
         }
+
+        uploadButton.setEnabled(checked);
     }
 
     @Override