Fixed an extra return opcode in empty functions

source/toy_compiler.c

@@ -1464,7 +1464,7 @@ static void writeBytecodeBody(Toy_Bytecode* mb, Toy_Ast* ast) {
 	writeBytecodeFromAst(&mb, ast);
 
 	//append an extra return if needed
-	if (mb->codeCount <= 4 || mb->code[mb->codeCount - 4] != TOY_OPCODE_RETURN) { //if empty or no return statement
+	if (mb->codeCount < 4 || mb->code[mb->codeCount - 4] != TOY_OPCODE_RETURN) { //if empty or no return statement
 		EMIT_BYTE(&mb, code, TOY_OPCODE_RETURN); //end terminator
 		EMIT_BYTE(&mb, code, 0); //4-byte alignment
 		EMIT_BYTE(&mb, code, 0);

tests/scripts/test_keyword_return.toy

@@ -1,8 +1,12 @@
 
-fn empty() { //BUG: there's an extra return in the bytecode
+fn empty() {
+	//
+}
+
+fn almostEmpty() {
 	return;
 }
 
-fn full() {
+fn notEmpty() {
 	return 42;
 }