Remove discareded NULL checks.

src/dump.c

@@ -889,9 +889,6 @@ mrb_dump_irep(mrb_state *mrb, mrb_irep *irep, int debug_info, uint8_t **bin, siz
               section_irep_size + section_lineno_size + section_lv_size +
               sizeof(struct rite_binary_footer);
   cur = *bin = (uint8_t*)mrb_malloc(mrb, *bin_size);
-  if (cur == NULL) {
-    goto error_exit;
-  }
   cur += sizeof(struct rite_binary_header);
 
   result = write_section_irep(mrb, irep, cur);

src/gc.c

@@ -229,9 +229,7 @@ mrb_calloc(mrb_state *mrb, size_t nelem, size_t len)
     size = nelem * len;
     p = mrb_realloc(mrb, 0, size);
 
-    if (p) {
-      memset(p, 0, size);
-    }
+    memset(p, 0, size);
   }
   else {
     p = NULL;