Fix CID 1393238 (Dereference null return value)

Add also some error handling if fopen fails.

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

Author: stweil

src/ccmain/control.cpp

@@ -128,8 +128,12 @@ bool Tesseract::ProcessTargetWord(const TBOX& word_box,
       if (backup_config_file_ == nullptr) {
         backup_config_file_ = kBackUpConfigFile;
         FILE* config_fp = fopen(backup_config_file_, "wb");
-        ParamUtils::PrintParams(config_fp, params());
-        fclose(config_fp);
+        if (config_fp == nullptr) {
+          tprintf("Error, failed to open file \"%s\"\n", backup_config_file_);
+        } else {
+          ParamUtils::PrintParams(config_fp, params());
+          fclose(config_fp);
+        }
         ParamUtils::ReadParamsFile(word_config,
                                    SET_PARAM_CONSTRAINT_DEBUG_ONLY,
                                    params());