drm/arm/malidp: fix a possible null pointer dereference

In malidp_mw_connector_reset, new memory is allocated with kzalloc, but
no check is performed. In order to prevent null pointer dereferencing,
ensure that mw_state is checked before calling
__drm_atomic_helper_connector_reset.

Fixes: 8cbc5caf36ef ("drm: mali-dp: Add writeback connector")
Signed-off-by: Huai-Yuan Liu <[e-mail]>
Signed-off-by: Liviu Dudau <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/arm/malidp_mw.c

···
 		__drm_atomic_helper_connector_destroy_state(connector->state);
 
 	kfree(connector->state);
-	__drm_atomic_helper_connector_reset(connector, &mw_state->base);
+	connector->state = NULL;
+
+	if (mw_state)
+		__drm_atomic_helper_connector_reset(connector, &mw_state->base);
 }
 
 static enum drm_connector_status