branch-to-fix-#9835 (#9840)

src/math/Vector2.js

@@ -87,6 +87,8 @@ Vector2.prototype = {
 			default: throw new Error( 'index is out of range: ' + index );
 
 		}
+		
+		return this;
 
 	},
 

src/math/Vector3.js

@@ -79,6 +79,8 @@ Vector3.prototype = {
 			default: throw new Error( 'index is out of range: ' + index );
 
 		}
+		
+		return this;
 
 	},
 

src/math/Vector4.js

@@ -86,6 +86,8 @@ Vector4.prototype = {
 			default: throw new Error( 'index is out of range: ' + index );
 
 		}
+		
+		return this;
 
 	},