@@ -198,7 +198,7 @@ private function getVisualizationSettings(
             return new GisVisualizationSettings(600, 450, $spatialCandidates[0]);
         }
 
-        $labelColumn = null;
+        $labelColumn = '';
         if (
             isset($settingsIn['labelColumn']) &&
             in_array($settingsIn['labelColumn'], $labelCandidates, true)
 
@@ -66,7 +66,7 @@ class GisVisualization
 
     private string $spatialColumn;
 
-    private string|null $labelColumn;
+    private string $labelColumn;
 
     public function getWidth(): int
     {
@@ -95,7 +95,7 @@ public function getSpatialColumn(): string
 
     public function getLabelColumn(): string|null
     {
-        return $this->labelColumn;
+        return $this->labelColumn === '' ? null : $this->labelColumn;
     }
 
     /**
@@ -202,7 +202,7 @@ private function modifySqlQuery(string $sqlQuery): string
         }
 
         // If label column is chosen add it to the query
-        if ($this->labelColumn !== null) {
+        if ($this->labelColumn !== '') {
             $modifiedQuery .= Util::backquote($this->labelColumn)
             . ', ';
         }
 
@@ -14,7 +14,7 @@ public function __construct(
         public int $width,
         public int $height,
         public string $spatialColumn,
-        public string|null $labelColumn = null,
+        public string $labelColumn = '',
     ) {
     }
 }
Original file line number	Diff line number	Diff line change
`@@ -198,7 +198,7 @@ private function getVisualizationSettings(`
`198`	`198`	`return new GisVisualizationSettings(600, 450, $spatialCandidates[0]);`
`199`	`199`	`}`
`200`	`200`
`201`		`- $labelColumn = null;`
	`201`	`+ $labelColumn = '';`
`202`	`202`	`if (`
`203`	`203`	`isset($settingsIn['labelColumn']) &&`
`204`	`204`	`in_array($settingsIn['labelColumn'], $labelCandidates, true)`
Original file line number	Diff line number	Diff line change
`@@ -66,7 +66,7 @@ class GisVisualization`
`66`	`66`
`67`	`67`	`private string $spatialColumn;`
`68`	`68`
`69`		`- private string\|null $labelColumn;`
	`69`	`+ private string $labelColumn;`
`70`	`70`
`71`	`71`	`public function getWidth(): int`
`72`	`72`	`{`
`@@ -95,7 +95,7 @@ public function getSpatialColumn(): string`
`95`	`95`
`96`	`96`	`public function getLabelColumn(): string\|null`
`97`	`97`	`{`
`98`		`- return $this->labelColumn;`
	`98`	`+ return $this->labelColumn === '' ? null : $this->labelColumn;`
`99`	`99`	`}`
`100`	`100`
`101`	`101`	`/**`
`@@ -202,7 +202,7 @@ private function modifySqlQuery(string $sqlQuery): string`
`202`	`202`	`}`
`203`	`203`
`204`	`204`	`// If label column is chosen add it to the query`
`205`		`- if ($this->labelColumn !== null) {`
	`205`	`+ if ($this->labelColumn !== '') {`
`206`	`206`	`$modifiedQuery .= Util::backquote($this->labelColumn)`
`207`	`207`	`. ', ';`
`208`	`208`	`}`
Original file line number	Diff line number	Diff line change
`@@ -14,7 +14,7 @@ public function __construct(`
`14`	`14`	`public int $width,`
`15`	`15`	`public int $height,`
`16`	`16`	`public string $spatialColumn,`
`17`		`- public string\|null $labelColumn = null,`
	`17`	`+ public string $labelColumn = '',`
`18`	`18`	`) {`
`19`	`19`	`}`
`20`	`20`	`}`