wsi/x11: fix uninit value

==767499== Conditional jump or move depends on uninitialised value(s)
==767499==    at 0xEB8E3ED: x11_image_finish (wsi_common_x11.c:1539)
==767499==    by 0xEB8E768: x11_swapchain_destroy (wsi_common_x11.c:1640)
==767499==    by 0xEB8A8FA: wsi_common_destroy_swapchain (wsi_common.c:505)
==767499==    by 0xDE30BA1: anv_DestroySwapchainKHR (anv_wsi.c:242)
==767499==    by 0x6817A21: copper_displaytarget_destroy (zink_copper.c:192)
==767499==    by 0x6882BE6: zink_destroy_resource_object (zink_resource.c:95)
==767499==    by 0x6882447: zink_resource_object_reference (zink_resource.h:198)
==767499==    by 0x6882D33: zink_resource_destroy (zink_resource.c:123)
==767499==    by 0x688AC97: pipe_resource_destroy (u_inlines.h:145)
==767499==    by 0x688AD2E: pipe_resource_reference (u_inlines.h:162)
==767499==    by 0x688BE1E: zink_destroy_surface (zink_surface.c:319)
==767499==    by 0x688AE0A: zink_surface_reference (zink_surface.h:102)
==767499==    by 0x688BE6D: zink_surface_destroy (zink_surface.c:328)
==767499==    by 0x67F9CA2: pipe_surface_release (u_inlines.h:134)
==767499==    by 0x67FB8AD: zink_context_destroy (zink_context.c:92)
==767499==    by 0x5D47B65: st_destroy_context_priv (st_context.c:475)
==767499==    by 0x5D49AF2: st_destroy_context (st_context.c:1193)
==767499==    by 0x5D5C90F: st_context_destroy (st_manager.c:816)
==767499==    by 0x5CC1FC9: dri_destroy_context (dri_context.c:248)
==767499==    by 0x658DD63: driDestroyContext (dri_util.c:535)
==767499==    by 0x5A30166: drisw_destroy_context (drisw_glx.c:417)
==767499==    by 0x5A32484: glXDestroyContext (glxcmds.c:515)
==767499==    by 0x5315AEB: glXDestroyContext (libglx.c:332)
==767499==    by 0x4AA8E7D: glXDestroyContext (g_libglglxwrapper.c:384)
==767499==    by 0x4D5A3F0: ??? (in /usr/lib64/libwaffle-1.so.0.6.1)
==767499==    by 0x499DDD5: piglit_wfl_framework_teardown (piglit_wfl_framework.c:638)
==767499==    by 0x499E4C5: piglit_winsys_framework_teardown (piglit_winsys_framework.c:238)
==767499==    by 0x499F50C: destroy (piglit_x11_framework.c:212)
==767499==    by 0x498C535: destroy (piglit-framework-gl.c:210)
==767499==    by 0x4F48AF6: __run_exit_handlers (in /usr/lib64/libc-2.33.so)
==767499==    by 0x4F48C9F: exit (in /usr/lib64/libc-2.33.so)
==767499==    by 0x4AEFD71: piglit_report_result (piglit-util.c:245)
==767499==    by 0x499F2CA: process_next_event (piglit_x11_framework.c:139)
==767499==    by 0x499F365: enter_event_loop (piglit_x11_framework.c:153)
==767499==    by 0x499DF88: run_test (piglit_winsys_framework.c:88)
==767499==    by 0x498C5EF: piglit_gl_test_run (piglit-framework-gl.c:229)
==767499==    by 0x4022B4: main (primitive-restart.c:45)
==767499==  Uninitialised value was created by a heap allocation
==767499==    at 0x484086F: malloc (vg_replace_malloc.c:380)
==767499==    by 0xE964E85: vk_default_alloc (vk_alloc.c:26)
==767499==    by 0xEB8B24B: vk_alloc (vk_alloc.h:43)
==767499==    by 0xEB8EAF9: x11_surface_create_swapchain (wsi_common_x11.c:1723)
==767499==    by 0xEB8A82A: wsi_common_create_swapchain (wsi_common.c:476)
==767499==    by 0xDE30B47: anv_CreateSwapchainKHR (anv_wsi.c:225)
==767499==    by 0xE96134F: vk_tramp_CreateSwapchainKHR (vk_dispatch_table.c:6592)
==767499==    by 0xD7B88F0: ??? (in /usr/lib64/libvulkan.so.1.2.162)
==767499==    by 0x6817796: copper_CreateSwapchain (zink_copper.c:123)
==767499==    by 0x6817960: copper_displaytarget_create (zink_copper.c:170)
==767499==    by 0x6884C65: resource_create (zink_resource.c:780)
==767499==    by 0x6884EC5: zink_resource_create_drawable (zink_resource.c:829)
==767499==    by 0x5CC0FE3: copper_allocate_textures (copper.c:199)
==767499==    by 0x5CC28C2: dri_st_framebuffer_validate (dri_drawable.c:82)
==767499==    by 0x5D5B69A: st_framebuffer_validate (st_manager.c:222)
==767499==    by 0x5D5D32D: st_api_make_current (st_manager.c:1102)
==767499==    by 0x5CC220B: dri_make_current (dri_context.c:306)
==767499==    by 0x658DE23: driBindContext (dri_util.c:588)
==767499==    by 0x5A3022A: drisw_bind_context (drisw_glx.c:435)
==767499==    by 0x5A36CC2: MakeContextCurrent (glxcurrent.c:220)
==767499==    by 0x5A36DF9: glXMakeCurrent (glxcurrent.c:253)
==767499==    by 0x531849C: InternalMakeCurrentVendor (libglx.c:875)
==767499==    by 0x53185C3: InternalMakeCurrentDispatch (libglx.c:930)
==767499==    by 0x5318DE5: CommonMakeCurrent (libglx.c:1074)
==767499==    by 0x5318ED5: glXMakeCurrent (libglx.c:1119)
==767499==    by 0x4AA9CFA: glXMakeCurrent (g_libglglxwrapper.c:930)
==767499==    by 0x4D5AA36: ??? (in /usr/lib64/libwaffle-1.so.0.6.1)
==767499==    by 0x4D5E16E: waffle_make_current (in /usr/lib64/libwaffle-1.so.0.6.1)
==767499==    by 0x499C8CD: wfl_checked_make_current (piglit-util-waffle.h:115)
==767499==    by 0x499DA04: make_context_current_singlepass (piglit_wfl_framework.c:488)
==767499==    by 0x499DC43: make_context_current (piglit_wfl_framework.c:565)
==767499==    by 0x499DD88: piglit_wfl_framework_init (piglit_wfl_framework.c:628)
==767499==    by 0x499E3FC: piglit_winsys_framework_init (piglit_winsys_framework.c:209)
==767499==    by 0x499F581: piglit_x11_framework_create (piglit_x11_framework.c:229)
==767499==    by 0x499E361: piglit_winsys_framework_factory (piglit_winsys_framework.c:175)
==767499==    by 0x498CA60: piglit_gl_framework_factory (piglit_gl_framework.c:53)
==767499==    by 0x498C587: piglit_gl_test_run (piglit-framework-gl.c:221)
==767499==    by 0x4022B4: main (primitive-restart.c:45)