shlwapi: Check an argument to UrlEscapeA.

dlls/shlwapi/tests/url.c

@@ -480,6 +480,11 @@ static void test_UrlEscape(void)
     }
 
     size = 1;
+    ret = UrlEscapeA("/woningplan/woonkamer basis.swf", empty_string, NULL, URL_ESCAPE_SPACES_ONLY);
+    ok(ret == E_INVALIDARG, "got %x, expected %x\n", ret, E_INVALIDARG);
+    ok(size == 1, "got %d, expected %d\n", size, 1);
+
+    size = 1;
     ret = UrlEscapeA("/woningplan/woonkamer basis.swf", empty_string, &size, URL_ESCAPE_SPACES_ONLY);
     todo_wine {
         ok(ret == E_POINTER, "got %x, expected %x\n", ret, E_POINTER);

dlls/shlwapi/url.c

@@ -843,6 +843,9 @@ HRESULT WINAPI UrlEscapeA(
     HRESULT ret;
     DWORD lenW = sizeof(bufW)/sizeof(WCHAR), lenA;
 
+    if (!pcchEscaped)
+        return E_INVALIDARG;
+
     if(!RtlCreateUnicodeStringFromAsciiz(&urlW, pszUrl))
         return E_INVALIDARG;
     if((ret = UrlEscapeW(urlW.Buffer, escapedW, &lenW, dwFlags)) == E_POINTER) {