gitclone: check for invalid patch filename

where the asterisk is used, it can sometimes
literally try to patch with a file named "*",
which of course does not exist

this change fixes an lbmk error when running:

./download seabios

this was caused recently, because all patches
were seabios were removed (lbmk currently uses
stock seabios, without patching it)

gitclone

@@ -35,6 +35,9 @@ Check_vars(){
 
 Patch(){
 	for patchfile in ${PWD}/${patchdir}/*.patch ; do
+		if [ ! -f "${patchfile}" ]; then
+			continue
+		fi
 		( cd ${tmp_dir}
 		git am ${patchfile} || return 1
 		)