Check project settings live before lookup in crash handler

In x11, windows and osx crash handlers, check project settings exists
before looking up the crash handler message setting.
Avoids crashing the crash handler when handling a crash outside project
settings lifetime. Instead omitting the configurable message and
continuing with trace dump.

platform/osx/crash_handler_osx.mm

@@ -77,7 +77,12 @@ static void handle_crash(int sig) {
 	void *bt_buffer[256];
 	size_t size = backtrace(bt_buffer, 256);
 	String _execpath = OS::get_singleton()->get_executable_path();
-	String msg = GLOBAL_GET("debug/settings/crash_handler/message");
+
+	String msg;
+	const ProjectSettings *proj_settings = ProjectSettings::get_singleton();
+	if (proj_settings) {
+		msg = proj_settings->get("debug/settings/crash_handler/message");
+	}
 
 	// Dump the backtrace to stderr with a message to the user
 	fprintf(stderr, "%s: Program crashed with signal %d\n", __FUNCTION__, sig);

platform/windows/crash_handler_windows.cpp

@@ -166,11 +166,16 @@ DWORD CrashHandlerException(EXCEPTION_POINTERS *ep) {
 	line.SizeOfStruct = sizeof(line);
 	IMAGE_NT_HEADERS *h = ImageNtHeader(base);
 	DWORD image_type = h->FileHeader.Machine;
-	int n = 0;
-	String msg = GLOBAL_GET("debug/settings/crash_handler/message");
+
+	String msg;
+	const ProjectSettings *proj_settings = ProjectSettings::get_singleton();
+	if (proj_settings) {
+		msg = proj_settings->get("debug/settings/crash_handler/message");
+	}
 
 	fprintf(stderr, "Dumping the backtrace. %ls\n", msg.c_str());
 
+	int n = 0;
 	do {
 		if (skip_first) {
 			skip_first = false;

platform/x11/crash_handler_x11.cpp

@@ -53,7 +53,12 @@ static void handle_crash(int sig) {
 	void *bt_buffer[256];
 	size_t size = backtrace(bt_buffer, 256);
 	String _execpath = OS::get_singleton()->get_executable_path();
-	String msg = GLOBAL_GET("debug/settings/crash_handler/message");
+
+	String msg;
+	const ProjectSettings *proj_settings = ProjectSettings::get_singleton();
+	if (proj_settings) {
+		msg = proj_settings->get("debug/settings/crash_handler/message");
+	}
 
 	// Dump the backtrace to stderr with a message to the user
 	fprintf(stderr, "%s: Program crashed with signal %d\n", __FUNCTION__, sig);