Core: Fix null pointer crash

build.bat

@@ -3,8 +3,8 @@ call "..\misc\compile_setup.bat"
 
 bld --dont_compile_core
 cd build
-rem core_main.exe rtsgame/main.core
-core_main.exe examples/unions.core
+core_main.exe rtsgame/main.core
+rem core_main.exe examples/unions.core
 bld --dont_compile_core --link=vendor/raylib/windows/raylibdll.lib
 rem build\generated_main.exe
 cd ..

core_codegen_c_language.cpp

@@ -582,7 +582,7 @@ gen_ast(Ast *ast) {
 
         CASE(RETURN, Return) {
             gen("return ");
-            gen_expr(node->expr);
+            if (node->expr) gen_expr(node->expr);
             gen(";");
             BREAK();
         }