diff --git a/tcpdf.php b/tcpdf.php
index 24ef434..a1b4c1c 100644
--- a/tcpdf.php
+++ b/tcpdf.php
@@ -18686,7 +18686,7 @@ Putting 1 is equivalent to putting 0 and calling Ln() just after. Default value:
 			$hbz = 0; // distance from y to line bottom
 			$hb = 0; // vertical space between block tags
 			// calculate vertical space for block tags
-			if (isset($this->tagvspaces[$tag['value']][0]['h']) AND ($this->tagvspaces[$tag['value']][0]['h'] >= 0)) {
+			if (isset($this->tagvspaces[$tag['value']][0]['h']) && !empty($this->tagvspaces[$tag['value']][0]['h']) && ($this->tagvspaces[$tag['value']][0]['h'] >= 0)) {
 				$cur_h = $this->tagvspaces[$tag['value']][0]['h'];
 			} elseif (isset($tag['fontsize'])) {
 				$cur_h = $this->getCellHeight($tag['fontsize'] / $this->k);
@@ -18718,7 +18718,7 @@ Putting 1 is equivalent to putting 0 and calling Ln() just after. Default value:
 			}
 			// closing vertical space
 			$hbc = 0;
-			if (isset($this->tagvspaces[$tag['value']][1]['h']) AND ($this->tagvspaces[$tag['value']][1]['h'] >= 0)) {
+			if (isset($this->tagvspaces[$tag['value']][1]['h']) && !empty($this->tagvspaces[$tag['value']][1]['h']) && ($this->tagvspaces[$tag['value']][1]['h'] >= 0)) {
 				$pre_h = $this->tagvspaces[$tag['value']][1]['h'];
 			} elseif (isset($parent['fontsize'])) {
 				$pre_h = $this->getCellHeight($parent['fontsize'] / $this->k);
@@ -19379,7 +19379,7 @@ Putting 1 is equivalent to putting 0 and calling Ln() just after. Default value:
 			$hbz = 0; // distance from y to line bottom
 			$hb = 0; // vertical space between block tags
 			// calculate vertical space for block tags
-			if (isset($this->tagvspaces[$tag['value']][1]['h']) AND ($this->tagvspaces[$tag['value']][1]['h'] >= 0)) {
+			if (isset($this->tagvspaces[$tag['value']][1]['h']) && !empty($this->tagvspaces[$tag['value']][1]['h']) && ($this->tagvspaces[$tag['value']][1]['h'] >= 0)) {
 				$pre_h = $this->tagvspaces[$tag['value']][1]['h'];
 			} elseif (isset($parent['fontsize'])) {
 				$pre_h = $this->getCellHeight($parent['fontsize'] / $this->k);