Fix an 'uninitialized value' warning.
diff --git a/tools/winapi_check/winapi_local.pm b/tools/winapi_check/winapi_local.pm
index 6513328..476da5c 100644
--- a/tools/winapi_check/winapi_local.pm
+++ b/tools/winapi_check/winapi_local.pm
@@ -119,7 +119,7 @@
} elsif($calling_convention =~ /^VFWAPIV|WINAPIV$/) {
$implemented_calling_convention = "varargs";
} elsif($calling_convention =~ /^__stdcall|VFWAPI|WINAPI|CALLBACK$/) {
- if($implemented_return_kind =~ /^s_word|word|void$/) {
+ if(defined($implemented_return_kind) && $implemented_return_kind =~ /^s_word|word|void$/) {
$implemented_calling_convention = "pascal16";
} else {
$implemented_calling_convention = "pascal";