LibRegex: Don't do out-of-bound match accesses when a test fails

Author: https://github.com/alimpfard
Commit: https://github.com/SerenityOS/serenity/commit/e5af15a6e91
Pull-request: https://github.com/SerenityOS/serenity/pull/8847
Reviewed-by: https://github.com/MaxWipfli
Reviewed-by: https://github.com/linusg ✅
Reviewed-by: https://github.com/trflynn89

Tests/LibRegex/Regex.cpp

@@ -458,10 +458,12 @@ TEST_CASE(a_star)
     String haystack = "[Window]\nOpacity=255\nAudibleBeep=0\n";
     EXPECT_EQ(re.search(haystack.view(), result, PosixFlags::Multiline), true);
     EXPECT_EQ(result.count, 32u);
-    EXPECT_EQ(result.matches.at(0).view.length(), 0u);
-    EXPECT_EQ(result.matches.at(10).view.length(), 1u);
-    EXPECT_EQ(result.matches.at(10).view, "a");
-    EXPECT_EQ(result.matches.at(31).view.length(), 0u);
+    if (result.count == 32u) {
+        EXPECT_EQ(result.matches.at(0).view.length(), 0u);
+        EXPECT_EQ(result.matches.at(10).view.length(), 1u);
+        EXPECT_EQ(result.matches.at(10).view, "a");
+        EXPECT_EQ(result.matches.at(31).view.length(), 0u);
+    }
 }
 
 TEST_CASE(simple_period_end_benchmark)
@@ -624,5 +626,7 @@ TEST_CASE(case_insensitive_match)
     auto result = re.match("AEKFCD");
 
     EXPECT_EQ(result.success, true);
-    EXPECT_EQ(result.matches.at(0).column, 4ul);
+    if (result.success) {
+        EXPECT_EQ(result.matches.at(0).column, 4ul);
+    }
 }