virgl/egl: fix null pointer dereference 1

Fixes https://gitlab.freedesktop.org/virgl/virglrenderer/issues/65

Reviewed-by Gert Wollny <gert.wollny@collabora.com>

src/virglrenderer.c

@@ -393,6 +393,9 @@ int virgl_renderer_init(void *cookie, int flags, struct virgl_renderer_callbacks
 int virgl_renderer_get_fd_for_texture(uint32_t tex_id, int *fd)
 {
 #ifdef HAVE_EPOXY_EGL_H
+   if (!egl)
+      return -1;
+
    return virgl_egl_get_fd_for_texture(egl, tex_id, fd);
 #else
    return -1;
@@ -402,6 +405,9 @@ int virgl_renderer_get_fd_for_texture(uint32_t tex_id, int *fd)
 int virgl_renderer_get_fd_for_texture2(uint32_t tex_id, int *fd, int *stride, int *offset)
 {
 #ifdef HAVE_EPOXY_EGL_H
+   if (!egl)
+      return -1;
+
    return virgl_egl_get_fd_for_texture2(egl, tex_id, fd, stride, offset);
 #else
    return -1;