fix(fabric.Text): Ensure the shortcut text render the passed argument…

… and not the entire line (fabricjs#6526)

src/shapes/text.class.js

@@ -878,13 +878,12 @@
 
     /**
      * @private
-     * @param {String} method
+     * @param {String} method fillText or strokeText.
      * @param {CanvasRenderingContext2D} ctx Context to render on
-     * @param {String} line Content of the line
+     * @param {Array} line Content of the line, splitted in an array by grapheme
      * @param {Number} left
      * @param {Number} top
      * @param {Number} lineIndex
-     * @param {Number} charOffset
      */
     _renderChars: function(method, ctx, line, left, top, lineIndex) {
       // set proper line offset
@@ -902,7 +901,7 @@
       top -= lineHeight * this._fontSizeFraction / this.lineHeight;
       if (shortCut) {
         // render all the line in one pass without checking
-        this._renderChar(method, ctx, lineIndex, 0, this.textLines[lineIndex], left, top, lineHeight);
+        this._renderChar(method, ctx, lineIndex, 0, line.join(''), left, top, lineHeight);
         ctx.restore();
         return;
       }