Applied fix found by BrainforgeUK in Issue #564 (#620)

Tested and confirmed working in PHP 7.4 and PHP 8.2

tcpdf.php

@@ -2461,7 +2461,7 @@ public function setLastH($h) {
 	 */
 	public function getCellHeight($fontsize, $padding=TRUE) {
 		$height = ($fontsize * $this->cell_height_ratio);
-		if ($padding) {
+		if ($padding && !empty($this->cell_padding)) {
 			$height += ($this->cell_padding['T'] + $this->cell_padding['B']);
 		}
 		return round($height, 6);