Fix another issue with gtest and is_open missing return value check

Author: LocutusOfBorg

tests/components/dlt-logd-converter/gtest_dlt_logd_converter.cpp

@@ -66,7 +66,8 @@ string t_load_json_file()
     char *token;
     string pattern;
     string json_sequence;
-    file.is_open();
+    if(!file.is_open())
+        return "";
     while (!file.eof()) {
         getline(file, pattern);
         if (pattern.size() == 0) {
@@ -590,4 +591,4 @@ TEST(t_logd_parser_loop, normal)
 int main(int argc, char** argv) {
     ::testing::InitGoogleTest(&argc, argv);
     return RUN_ALL_TESTS();
-}
+}