fix(converters): Fix default param in converters

Fixed the default parameter assigment in converters that was crashing in ES5.

Author: Alexandru Badiu

README.md

@@ -17,7 +17,7 @@ Node image generation module based on [sharp](https://github.com/lovell/sharp) a
 
 ```
 import presets from './presets';
-import ImageCache from 'imagecache';
+import ImageCache from 'imagecache-sharp';
 
 const imagecache = new ImageCache(presets);
 

dist/plugins/_converters.js

@@ -23,9 +23,11 @@ module.exports = {
       return converted;
     };
 
-    app.actions.convertPosition = (value, maxPosition, imageSize = 0) => {
+    app.actions.convertPosition = (value, maxPosition, imageSize) => {
       let converted;
 
+      imageSize = imageSize || 0;
+
       if (value === 'left' || value === 'top') {
         converted = 0;
       } else if (value === 'center') {

src/plugins/_converters.js

@@ -21,9 +21,11 @@ module.exports = {
       return converted;
     };
 
-    app.actions.convertPosition = (value, maxPosition, imageSize = 0) => {
+    app.actions.convertPosition = (value, maxPosition, imageSize) => {
       let converted;
 
+      imageSize = imageSize || 0;
+
       if (value === 'left' || value === 'top') {
         converted = 0;
       } else if (value === 'center') {