oleaut32: Don't crash on NULL string arguments.

dlls/oleaut32/tests/typelib.c

@@ -4243,6 +4243,8 @@ static void test_SetFuncAndParamNames(void)
     static OLECHAR nameW[] = {'n','a','m','e',0};
     static OLECHAR prop[] = {'p','r','o','p',0};
     static OLECHAR *propW[] = {prop};
+    static OLECHAR func[] = {'f','u','n','c',0};
+    static OLECHAR *funcW[] = {func, NULL};
     CHAR filenameA[MAX_PATH];
     WCHAR filenameW[MAX_PATH];
     ICreateTypeLib2 *ctl;
@@ -4309,6 +4311,15 @@ static void test_SetFuncAndParamNames(void)
     hr = ICreateTypeInfo_SetFuncAndParamNames(cti, 3, propW, 1);
     ok(hr == TYPE_E_AMBIGUOUSNAME, "got 0x%08x\n", hr);
 
+    /* regular function */
+    funcdesc.invkind = INVOKE_FUNC;
+    funcdesc.cParams = 1;
+    hr = ICreateTypeInfo_AddFuncDesc(cti, 4, &funcdesc);
+    ok(hr == S_OK, "got 0x%08x\n", hr);
+
+    hr = ICreateTypeInfo_SetFuncAndParamNames(cti, 4, funcW, 2);
+    ok(hr == S_OK, "got 0x%08x\n", hr);
+
     ICreateTypeInfo_Release(cti);
     ICreateTypeLib2_Release(ctl);
     DeleteFileA(filenameA);

dlls/oleaut32/typelib.c

@@ -1889,6 +1889,9 @@ static TLBString *TLB_append_str(struct list *string_list, BSTR new_str)
 {
     TLBString *str;
 
+    if(!new_str)
+        return NULL;
+
     LIST_FOR_EACH_ENTRY(str, string_list, TLBString, entry) {
         if (strcmpW(str->str, new_str) == 0)
             return str;