Merge pull request #20167 from Mugen87/dev44

WebGLExtension: Fix return value of `has()`.

src/renderers/webgl/WebGLExtensions.d.ts

@@ -2,6 +2,7 @@ export class WebGLExtensions {
 
 	constructor( gl: WebGLRenderingContext );
 
+	has( name: string ): boolean;
 	get( name: string ): any;
 
 }

src/renderers/webgl/WebGLExtensions.js

@@ -8,7 +8,7 @@ function WebGLExtensions( gl ) {
 
 			if ( extensions[ name ] !== undefined ) {
 
-				return extensions[ name ];
+				return extensions[ name ] !== null;
 
 			}
 
@@ -39,7 +39,7 @@ function WebGLExtensions( gl ) {
 
 			extensions[ name ] = extension;
 
-			return !! extension;
+			return extension !== null;
 
 		},