media: ti-vpe: cal: Fix a NULL pointer dereference in cal_ctx_v4l2_init_formats()

In cal_ctx_v4l2_init_formats(), devm_kzalloc() is assigned to
ctx->active_fmt and there is a dereference of it after that, which could
lead to NULL pointer dereference on failure of devm_kzalloc().

Fix this bug by adding a NULL check of ctx->active_fmt.

This bug was found by a static analyzer.

Builds with 'make allyesconfig' show no new warnings, and our static
analyzer no longer warns about this code.

Fixes: 71681550 ("media: ti-vpe: cal: Move format handling to cal.c and expose helpers")
Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/platform/ti-vpe/cal-video.c

@@ -823,6 +823,9 @@ static int cal_ctx_v4l2_init_formats(struct cal_ctx *ctx)
 	/* Enumerate sub device formats and enable all matching local formats */
 	ctx->active_fmt = devm_kcalloc(ctx->cal->dev, cal_num_formats,
 				       sizeof(*ctx->active_fmt), GFP_KERNEL);
+	if (!ctx->active_fmt)
+		return -ENOMEM;
+
 	ctx->num_active_fmt = 0;
 
 	for (j = 0, i = 0; ; ++j) {