Fixes #36873: Do not return undefined from `_readPixelOffset`

src/vs/editor/browser/viewParts/lines/viewLine.ts

@@ -397,7 +397,7 @@ class RenderedViewLine implements IRenderedViewLine {
 
 		this._pixelOffsetCache = null;
 		if (!containsRTL || this._characterMapping.length === 0 /* the line is empty */) {
-			this._pixelOffsetCache = new Int32Array(this._characterMapping.length + 1);
+			this._pixelOffsetCache = new Int32Array(Math.max(2, this._characterMapping.length + 1));
 			for (let column = 0, len = this._characterMapping.length; column <= len; column++) {
 				this._pixelOffsetCache[column] = -1;
 			}