Only define *existing* methods, when converting the OPS format to method-names on the CanvasGraphics.prototype

There's no good reason, as far as I can tell, to explicitly define a bunch of methods to be `undefined`, which the current unconditional "copying" of methods will do.
Note that of the `OPS` ~23 percent don't, for various reasons, have an associated method on the `CanvasGraphics.prototype`.

src/display/canvas.js

@@ -2804,7 +2804,9 @@ class CanvasGraphics {
 }
 
 for (const op in OPS) {
-  CanvasGraphics.prototype[OPS[op]] = CanvasGraphics.prototype[op];
+  if (CanvasGraphics.prototype[op] !== undefined) {
+    CanvasGraphics.prototype[OPS[op]] = CanvasGraphics.prototype[op];
+  }
 }
 
 export { CanvasGraphics };