bugfix(system): Add defensive check in extractCrashLocation for empty strings

Add null and empty string checks after calling g_LastErrorDump.str() to
handle cases where isEmpty() doesn't work reliably across different build
configurations and STL implementations.

Issue discovered in testing: Location field showed different values across builds
when calling ReleaseCrash() without exception context:
- Win32 Release: Empty (correct)
- VC6 Release: Shows 'T' (incorrect - isEmpty() failed)
- Win32 Debug: Shows corrupted data (incorrect - isEmpty() failed)

The additional check ensures consistent behavior across all builds.
This doesn't affect real crashes - exceptions always populate g_LastErrorDump
through DumpExceptionInfo() which properly clears and fills the string.

Relates to TheSuperHackers#2069

Author: JohnsterID

Core/GameEngine/Source/Common/System/Debug.cpp

@@ -757,6 +757,13 @@ static void extractCrashLocation(char* outBuffer, size_t bufferSize)
 
 	const char* stackStr = g_LastErrorDump.str();
 
+	// TheSuperHackers @bugfix JohnsterID 12/01/2026 Defensive check for null or empty string
+	// isEmpty() check above doesn't work reliably across all build configs (VC6/STLPort vs Win32).
+	// This ensures consistent behavior when ReleaseCrash called without exception context.
+	if (!stackStr || !*stackStr) {
+		return;
+	}
+
 	// Skip leading whitespace/newlines
 	while (*stackStr && isspace(static_cast<unsigned char>(*stackStr))) {
 		stackStr++;