[gnc-filepath-utils.cpp] null check char* arguments

libgnucash/core-utils/gnc-filepath-utils.cpp

@@ -1326,6 +1326,7 @@ backup_regex (".*[.](?:xac|gnucash)[.][0-9]{14}[.](?:xac|gnucash)$");
 
 gboolean gnc_filename_is_backup (const char *filename)
 {
+    g_return_val_if_fail (filename, FALSE);
     return std::regex_match (filename, backup_regex);
 }
 
@@ -1334,6 +1335,7 @@ datafile_regex (".*[.](?:xac|gnucash)$");
 
 gboolean gnc_filename_is_datafile (const char *filename)
 {
+    g_return_val_if_fail (filename, FALSE);
     return !gnc_filename_is_backup (filename) &&
         std::regex_match (filename, datafile_regex);
 }

libgnucash/core-utils/test/gtest-path-utilities.cpp

@@ -141,10 +141,12 @@ TEST_F(PathTest, gnc_path_get_sysconfdir)
 
 TEST_F (PathTest, gnc_filename_is_backup)
 {
+    EXPECT_EQ (gnc_filename_is_backup (nullptr), false);
     EXPECT_EQ (gnc_filename_is_backup (""), false);
     EXPECT_EQ (gnc_filename_is_backup ("a.gnucash"), false);
     EXPECT_EQ (gnc_filename_is_backup ("a.gnucash.20201131010203.gnucash"), true);
 
+    EXPECT_EQ (gnc_filename_is_datafile (nullptr), false);
     EXPECT_EQ (gnc_filename_is_datafile (""), false);
     EXPECT_EQ (gnc_filename_is_datafile ("a.gnucash"), true);
     EXPECT_EQ (gnc_filename_is_datafile ("a.gnucash.20201131010203.gnucash"), false);