Do not dereference a null dialog when the optional hyprland-dialog utility is
not installed.

Index: src/Compositor.cpp
--- src/Compositor.cpp.orig
+++ src/Compositor.cpp
@@ -74,7 +74,6 @@
 #include <sys/stat.h>
 #include <sys/resource.h>
 #include <sys/ioctl.h>
-#include <malloc.h>
 #include <unistd.h>
 #include <xf86drm.h>
 
@@ -918,6 +917,11 @@ void CCompositor::openSafeModeBox() {
                                                  OPT_OPEN,
                                                  OPT_OK,
                                              });
+
+    if (!box) {
+        Log::logger->log(Log::ERR, "Unable to open the safe mode dialog: hyprland-dialog is not installed");
+        return;
+    }
 
     box->open()->then([OPT_LOAD, OPT_OK, OPT_OPEN, this](SP<CPromiseResult<std::string>> result) {
         if (result->hasError())
