fix: warnings fix (after -Wall -Wextra)

src/vm/fzl_vm.c

@@ -650,8 +650,17 @@ int fzl_vm_run(fzl_vm_t *vm)
         break;
 
       case FZL_OPCODE_JMP:
-        vm->ip = vm->ops[++vm->ip] - 1;
+      {
+        if (vm->ops_count >= vm->ip)
+        {
+          snprintf(last_err, sizeof(last_err),
+                   "runtime error - expected JMP addr");
+          return -1;
+        }
+        uint64_t jmp_ip = vm->ops[++vm->ip];
+        vm->ip          = jmp_ip - 1;
         break;
+      }
 
       case FZL_OPCODE_AND:
         if (vm->dtop < 2)

src/vm/fzl_vm_env.c

@@ -7,8 +7,6 @@
 #include <string.h>
 #include <vm/fzl_vm_env.h>
 
-static const fzl_value_t null = {.type = FZL_TYPE_NULL};
-
 fzl_vm_env_t *fzl_mkenv()
 {
   fzl_vm_env_t *env = malloc(sizeof(fzl_vm_env_t));

src/vm/main.c

@@ -33,7 +33,7 @@ run_args_t *parse_args(int argc, char **argv)
   args->help       = false;
   args->debug      = false;
 
-  for (size_t i = 0; i < argc; i++)
+  for (int i = 0; i < argc; i++)
   {
     if (argv[i][0] != '-')
       continue;