Check for NULL path argument in DeleteFile.

files/file.c

diff --git a/files/file.c b/files/file.c
index 0993492..02ff517 100644
--- a/files/file.c
+++ b/files/file.c
@@ -1934,6 +1934,11 @@
 {
     DOS_FULL_NAME full_name;
 
+    if (!path)
+    {
+        SetLastError(ERROR_INVALID_PARAMETER);
+        return FALSE;
+    }
     TRACE("'%s'\n", path );
 
     if (!*path)