fix set uniform value

Author: sunag

src/renderers/common/extras/PMREMGenerator.js

@@ -622,7 +622,7 @@ class PMREMGenerator {
 		blurMesh.material = blurMaterial;
 
 		targetIn.texture.frame = ( targetIn.texture.frame || 0 ) + 1;
-		blurMaterial._envMap = targetIn.texture
+		blurMaterial._envMap.value = targetIn.texture
 
 		const { _lodMax } = this;
 		const {radiansPerPixel, samples, weights}=getBlurParams(sigmaRadians, this._sizeLods[ lodIn ] - 1, MAX_SAMPLES);