Ensure pty gets resize event on layout

Fixes #28138

src/vs/workbench/parts/terminal/electron-browser/terminalInstance.ts

@@ -761,13 +761,15 @@ export class TerminalInstance implements ITerminalInstance {
 			this._xterm.resize(this._cols, this._rows);
 			this._xterm.element.style.width = terminalWidth + 'px';
 		}
-		if (this._process.connected) {
+		this._processReady.then(() => {
+			if (this._process) {
 				this._process.send({
 					event: 'resize',
 					cols: this._cols,
 					rows: this._rows
 				});
 			}
+		});
 	}
 
 	public enableApiOnData(): void {