p5shader - beginShape(POINTS | LINES) ignores custom shaders

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
• IO (Input/Output)
• Localization
• Math
• Unit Testing
• Typography
• Utilities
• WebGL
• Other (specify if possible)

Details about the bug:

• p5.js version: 1.2.0
• Web browser and version: Chrome 89.0.4389.90
• Operating System: Windows 10 Home Premium
• Steps to reproduce this: Vertices defined between beginShape(arg) and endShape() with arg = LINES | POINTS are not passed to custom shaders previously loaded and set with loadShader() and shader() functions.

`let theShader;
let mycube = null;
let activeCam;

function preload(){

theShader = loadShader('shader.vert', 'shader.frag');
}

function setup() {
createCanvas(600,600,WEBGL);
angleMode(DEGREES);
activeCam = _createCamera();
activeCam.apply();
mycube = _createCube();
}

function draw() {

shader(theShader);
activeCam.move();
scale(1,-1,1);
background(200)

theShader.setUniform('uSizeFactor', 10.0);
theShader.setUniform('uMorphFactor', math.abs(math.cos(millis() / 1000)));

//noFill();
//noStroke();
mycube.render(); // renders a cube with beginShape() / endShape()
}`

Start by reproducing the supplied WebGL sketch and tracing how beginShape(POINTS | LINES), endShape(), loadShader(), and shader() interact when vertices are rendered. Confirm the behavior for both POINTS and LINES, then verify that custom shaders receive those vertices as expected without changing the existing rendering behavior.