Don't freak out if one of the pics hasn't loaded

Instead of throwing up hands in despair, Seance will now simply
ignore the badly loaded image and carry on.

seance.js

@@ -8,6 +8,7 @@ const { createClient } = require('webdav')
 const readline = require('readline')
 const { markdown } = require('markdown')
 const GhostAdminAPI = require('@tryghost/admin-api')
+const { Canvas, Image } = require('canvas')
 const Rembrandt = require('rembrandt')
 
 const config = require('./config')
@@ -389,6 +390,25 @@ class Seance {
       return false
     } else {
 
+      /* First, check that the image has finished loading
+       * (we don't use this, because Rembrandt loads it again
+       * on its own, which is messy but what to do ¯\_(ツ)_/¯
+       */
+
+      try {
+        let ctx = new Canvas().getContext('2d')
+        let img = new Image()
+        img.src = imagePath
+        ctx.drawImage(img, 0, 0, img.width, img.height)
+      } catch (err) {
+        this.emit('update', {
+            status: 'normal',
+            message: `[scissors] Skipping scissors check:${err.message}`,
+            loglevel: 'warning'
+          })
+          return false
+      }
+
       // Check if given image matches the scissors
       try {
         let isScissors = new Rembrandt({