ima: Pass NULL instead of 0 to ima_get_action() in ima_file_mprotect()

This patch fixes the sparse warning:

sparse: warning: Using plain integer as NULL pointer
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

security/integrity/ima/ima_main.c

@@ -433,7 +433,7 @@ int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot)
 	inode = file_inode(vma->vm_file);
 	action = ima_get_action(file_mnt_user_ns(vma->vm_file), inode,
 				current_cred(), secid, MAY_EXEC, MMAP_CHECK,
-				&pcr, &template, 0);
+				&pcr, &template, NULL);
 
 	/* Is the mmap'ed file in policy? */
 	if (!(action & (IMA_MEASURE | IMA_APPRAISE_SUBMASK)))