fix: API cartes statiques

éviter de générer du vide quand certaines tuiles de la carte passent la date crossing line

inspiré de e5a3aee344 & 4ae1ebd7e9/mapbox.js (L27)

inc/staticmap.php

@@ -241,8 +241,13 @@ class staticMapGis
 		$this->offsetY += floor($startY - floor($this->centerY)) * $this->tileSize;
 
 		for ($x = $startX; $x <= $endX; $x++) {
+			// normalise x index for tile stitching at date crossing line
+			$xNorm = $x % (2 ** $this->zoom);
+			if ($xNorm < 0) {
+				$xNorm = $xNorm + (2 ** $this->zoom);
+			}
 			for ($y = $startY; $y <= $endY; $y++) {
-				$url = str_replace(['{Z}', '{X}', '{Y}'], [$this->zoom, $x, $y], $this->tileSrcUrl[$this->maptype]['url']);
+				$url = str_replace(['{Z}', '{X}', '{Y}'], [$this->zoom, $xNorm, $y], $this->tileSrcUrl[$this->maptype]['url']);
 				$tileData = $this->fetchTile($url);
 				if ($tileData) {
 					$tileImage = @imagecreatefromstring($tileData);