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

In the Linux kernel, the following vulnerability has been resolved: 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.