Error when using loadJSON should catch error and not stop the process if there is an errorCallback

[dievardump]

Most appropriate sub-area of p5.js?

• [ ] Accessibility (Web Accessibility)
• [ ] Build tools and processes
• [ ] Color
• [ ] Core/Environment/Rendering
• [ ] Data
• [ ] DOM
• [ ] Events
• [ ] Friendly error system
• [ ] Image
• [x] IO (Input/Output)
• [ ] Localization
• [ ] Math
• [ ] Unit Testing
• [ ] Typography
• [ ] Utilities
• [ ] WebGL
• [ ] Other (specify if possible)

Details about the bug:

• p5.js version: 1.3.1
• Web browser and version: Firefox 88.0.1
• Operating System: Linux
• Steps to reproduce this:

  
  let meta = { 
  // default value
  metadata: {}
  };

function preload() { const uri = 'unknown.json';

function onLoad(data) { meta.metadata = data; }

function onError(error) { console.log(error); }

loadJSON(uri, onLoad, onError); }

function setup() { createcanvas(windowWidth, windowHeight); fill(255); rect(0, 0, 250, 250); }

I am trying to fetch a file. This file can be present or not, therefore I have default data already set. 

Since I provide an `onError` callback, It explicitly means that I wish to handle the error myself. I expect the error to be catched and passed to the onError callback, without stopping the current process.

However, here, the error is passed to onError but is not catched, so it propagates and stop everything from working.

[limzykenneth]

Possibly related to #5032

[chepecarlos]

same error in version 1.6.0