WebGLRenderer: Fixed MorphTargets breakage.

When multiple morphTargets where in the same scene, this optimization resulted in a mix of morphTargets from different animations with different sizes.

src/renderers/WebGLRenderer.js

@@ -3143,11 +3143,7 @@ THREE.WebGLRenderer = function ( parameters ) {
 
 				influence = influences[ i ];
 
-				if ( influence !== 0 ) {
-
-					activeInfluenceIndices.push( [ influence, i ] );
-
-				}
+				activeInfluenceIndices.push( [ influence, i ] );
 
 			}