Setting text on Konva.Text, treat undefined width or height as 'auto'

Similar to how it's handled in getWidth() and getHeight() of Konva.Text,
let _setTextData() treat undefined values of the 'width' and 'height'
attributes as if they are set to 'auto', not as if they are fixed.

src/shapes/Text.ts

@@ -342,8 +342,8 @@ export class Text extends Shape {
       lineHeightPx = this.lineHeight() * fontSize,
       width = this.attrs.width,
       height = this.attrs.height,
-      fixedWidth = width !== AUTO,
-      fixedHeight = height !== AUTO,
+      fixedWidth = width !== AUTO && width !== undefined,
+      fixedHeight = height !== AUTO && height !== undefined,
       padding = this.padding(),
       maxWidth = width - padding * 2,
       maxHeightPx = height - padding * 2,