Don't use NULL for integer arguments

This fixes compiler warnings:

api/baseapi.cpp:1422:49: warning:
 passing NULL to non-pointer argument 6 of
 'int MultiByteToWideChar(UINT, DWORD, LPCCH, int, LPWSTR, int)'
 [-Wconversion-null]
api/baseapi.cpp:1427:54:
 warning: passing NULL to non-pointer argument 6 of
 'int WideCharToMultiByte(UINT, DWORD, LPCWCH, int, LPSTR, int, LPCCH, LPBOOL)'
 [-Wconversion-null]

Signed-off-by: Stefan Weil <sw@weilnetz.de>

api/baseapi.cpp

@@ -1419,12 +1419,12 @@ char* TessBaseAPI::GetHOCRText(int page_number) {
 #ifdef _WIN32
   // convert input name from ANSI encoding to utf-8
   int str16_len = MultiByteToWideChar(CP_ACP, 0, input_file_->string(), -1,
-                                      NULL, NULL);
+                                      NULL, 0);
   wchar_t *uni16_str = new WCHAR[str16_len];
   str16_len = MultiByteToWideChar(CP_ACP, 0, input_file_->string(), -1,
                                   uni16_str, str16_len);
   int utf8_len = WideCharToMultiByte(CP_UTF8, 0, uni16_str, str16_len, NULL,
-                                     NULL, NULL, NULL);
+                                     0, NULL, NULL);
   char *utf8_str = new char[utf8_len];
   WideCharToMultiByte(CP_UTF8, 0, uni16_str, str16_len, utf8_str,
                       utf8_len, NULL, NULL);