WebGLPrograms: Fixed warning spamming for WebGL1 users.

src/renderers/webgl/WebGLPrograms.js

@@ -266,9 +266,9 @@ function WebGLPrograms( renderer, cubemaps, extensions, capabilities, bindingSta
 			extensionDrawBuffers: material.extensions && material.extensions.drawBuffers,
 			extensionShaderTextureLOD: material.extensions && material.extensions.shaderTextureLOD,
 
-			rendererExtensionFragDepth: isWebGL2 || extensions.get( 'EXT_frag_depth' ) !== null,
-			rendererExtensionDrawBuffers: isWebGL2 || extensions.get( 'WEBGL_draw_buffers' ) !== null,
-			rendererExtensionShaderTextureLod: isWebGL2 || extensions.get( 'EXT_shader_texture_lod' ) !== null,
+			rendererExtensionFragDepth: isWebGL2 || extensions.has( 'EXT_frag_depth' ),
+			rendererExtensionDrawBuffers: isWebGL2 || extensions.has( 'WEBGL_draw_buffers' ),
+			rendererExtensionShaderTextureLod: isWebGL2 || extensions.has( 'EXT_shader_texture_lod' ),
 
 			customProgramCacheKey: material.customProgramCacheKey()