fixed input slider target update rendering

thanks, @jadga-h , for the bug report!

HISTORY.md

@@ -6,6 +6,7 @@
 * morphic, blocks, gui: tweaked block-fading mouse-over
 * blocks, threads: tweaked context visualizations to be alpha-independent
 * gui: save block-transparency in  settings 
+* morphic: fixed input slider target update rendering
 
 ### 2020-07-21
 * blocks: tweaked block highlights for fade-out

src/morphic.js

@@ -12617,6 +12617,7 @@ WorldMorph.prototype.slide = function (aStringOrTextMorph) {
     slider.action = (num) => {
         aStringOrTextMorph.changed();
         aStringOrTextMorph.text = Math.round(num).toString();
+        aStringOrTextMorph.fixLayout();
         aStringOrTextMorph.rerender();
         aStringOrTextMorph.escalateEvent(
             'reactToSliderEdit',