dri: fix image_loader_extensions array

NULL was forgotten.

This issue was detected by the gcc sanitizer.

==30873==ERROR: AddressSanitizer: global-buffer-overflow on address 0x7f94f9ad14b0 at pc 0x7f94f04905bc bp 0x7ffe3b1ebcf0 sp 0x7ffe3b1ebce8
READ of size 8 at 0x7f94f9ad14b0 thread T0
    #0 0x7f94f04905bb in loader_bind_extensions ../src/loader/loader.c:783
    #1 0x7f94ee656232 in setupLoaderExtensions ../src/gallium/frontends/dri/dri_util.c:88
    #2 0x7f94ee656232 in driCreateNewScreen3 ../src/gallium/frontends/dri/dri_util.c:111
    #3 0x7f94f98d9a14 in dri2_create_screen ../src/egl/drivers/dri2/egl_dri2.c:774
    #4 0x7f94f98dfbea in surfaceless_probe_device ../src/egl/drivers/dri2/platform_surfaceless.c:298
    #5 0x7f94f98dfbea in dri2_initialize_surfaceless ../src/egl/drivers/dri2/platform_surfaceless.c:390
    #6 0x7f94f98dbc4f in dri2_initialize ../src/egl/drivers/dri2/egl_dri2.c:861
    #7 0x7f94f98dbc4f in dri2_initialize ../src/egl/drivers/dri2/egl_dri2.c:832
    #8 0x7f94f9892843 in eglInitialize ../src/egl/main/eglapi.c:696

Fixes: 56ed5cf ("dri: Get rid of __DRIbackgroundCallableExtension")
Signed-off-by: Patrick Lerda <[email protected]>
Reviewed-by: Eric Engestrom <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36255>
(cherry picked from commit 92dc71d)

Author: Patrick Lerda

.pick_status.json

@@ -1454,7 +1454,7 @@
         "description": "dri: fix image_loader_extensions array",
         "nominated": true,
         "nomination_type": 2,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "56ed5cf1bba0304d258a56d0f9c2e767705cec01",
         "notes": null

src/egl/drivers/dri2/platform_surfaceless.c

@@ -207,7 +207,7 @@ static const __DRIimageLoaderExtension image_loader_extension = {
 };
 
 static const __DRIextension *image_loader_extensions[] = {
-   &image_loader_extension.base,  &image_lookup_extension.base,
+   &image_loader_extension.base,  &image_lookup_extension.base, NULL,
 };
 
 static const __DRIextension *swrast_loader_extensions[] = {