Fix many asan and ubsan reported issues

This allows most demos to run without any ubsan or asan errors. There
are still some things in thirdpart/ and some things in AudioServer that
needs a look but this fixes a lot of issues. This should help debug less
obvious issues, hopefully.

This fixes #25217 and fixes #25218

modules/gdscript/gdscript_parser.cpp

@@ -4553,6 +4553,7 @@ void GDScriptParser::_parse_class(ClassNode *p_class) {
 				//variale declaration and (eventual) initialization
 
 				ClassNode::Member member;
+
 				bool autoexport = tokenizer->get_token(-1) == GDScriptTokenizer::TK_PR_EXPORT;
 				if (current_export.type != Variant::NIL) {
 					member._export = current_export;
@@ -5594,6 +5595,9 @@ GDScriptParser::DataType GDScriptParser::_type_from_gdtype(const GDScriptDataTyp
 	result.script_type = p_gdtype.script_type;
 
 	switch (p_gdtype.kind) {
+		case GDScriptDataType::UNINITIALIZED: {
+			ERR_EXPLAIN("Uninitialized datatype. Please report a bug.");
+		} break;
 		case GDScriptDataType::BUILTIN: {
 			result.kind = DataType::BUILTIN;
 		} break;