allow freeing NULL pixmap masks

diff --git a/render/mask.c b/render/mask.c
index 26059ca6e581bb1c6696a9be976b546d5850eaa9..22cb3feeb96c5879b485503fbf07c545e7df80b6 100644 (file)
--- a/render/mask.c
+++ b/render/mask.c
@@ -14,9 +14,11 @@ pixmap_mask *pixmap_mask_new(int w, int h, char *data)
 
 void pixmap_mask_free(pixmap_mask *m)
 {
-    XFreePixmap(ob_display, m->mask);
-    g_free(m->data);
-    g_free(m);
+    if (m) {
+        XFreePixmap(ob_display, m->mask);
+        g_free(m->data);
+        g_free(m);
+    }
 }
 
 void mask_draw(Pixmap p, TextureMask *m, Rect *position)