Cleanup: DRW: Replace 0 by NULL in GPU_context_create calls

This was left from a previous refactor.

source/blender/draw/engines/eevee/eevee_lightcache.c

@@ -526,7 +526,7 @@ static void eevee_lightbake_context_enable(EEVEE_LightBake *lbake)
   if (lbake->gl_context) {
     DRW_opengl_render_context_enable(lbake->gl_context);
     if (lbake->gpu_context == NULL) {
-      lbake->gpu_context = GPU_context_create(0);
+      lbake->gpu_context = GPU_context_create(NULL);
     }
     DRW_gpu_render_context_enable(lbake->gpu_context);
   }

source/blender/draw/intern/draw_manager.c

@@ -2771,7 +2771,7 @@ void DRW_opengl_context_create(void)
   DST.gl_context = WM_opengl_context_create();
   WM_opengl_context_activate(DST.gl_context);
   /* Be sure to create gpu_context too. */
-  DST.gpu_context = GPU_context_create(0);
+  DST.gpu_context = GPU_context_create(NULL);
   /* So we activate the window's one afterwards. */
   wm_window_reset_drawable();
 }

source/blender/draw/tests/shaders_test.cc

@@ -27,7 +27,7 @@ class DrawTest : public ::testing::Test {
     GHOST_GLSettings glSettings = {0};
     ghost_system = GHOST_CreateSystem();
     ghost_context = GHOST_CreateOpenGLContext(ghost_system, glSettings);
-    context = GPU_context_create(0);
+    context = GPU_context_create(NULL);
     GPU_init();
     DRW_draw_state_init_gtests(GPU_SHADER_CFG_DEFAULT);
   }

source/blender/render/intern/source/pipeline.c

@@ -1113,7 +1113,7 @@ void *RE_gl_context_get(Render *re)
 void *RE_gpu_context_get(Render *re)
 {
   if (re->gpu_context == NULL) {
-    re->gpu_context = GPU_context_create(0);
+    re->gpu_context = GPU_context_create(NULL);
   }
   return re->gpu_context;
 }