diff --git a/common.php b/common.php
index 66c689206..2d37ec68e 100644
--- a/common.php
+++ b/common.php
@@ -276,7 +276,7 @@ function clean_filename($fname)
  */
 function str_compact($str)
 {
-    return preg_replace('#\s+#u', ' ', trim($str));
+    return preg_replace('#\s+#u', ' ', trim($str ?? ''));
 }
 
 /**
diff --git a/src/Legacy/SqlDb.php b/src/Legacy/SqlDb.php
index 9696535b6..280778ccb 100644
--- a/src/Legacy/SqlDb.php
+++ b/src/Legacy/SqlDb.php
@@ -1012,7 +1012,7 @@ class SqlDb
                 $this->explain_hold .= '<tr>';
                 foreach (array_values($row) as $i => $val) {
                     $class = !($i % 2) ? 'row1' : 'row2';
-                    $this->explain_hold .= '<td class="' . $class . ' gen">' . str_replace(["{$this->selected_db}.", ',', ';'], ['', ', ', ';<br />'], $val) . '</td>';
+                    $this->explain_hold .= '<td class="' . $class . ' gen">' . str_replace(["{$this->selected_db}.", ',', ';'], ['', ', ', ';<br />'], $val ?? '') . '</td>';
                 }
                 $this->explain_hold .= '</tr>';