If qemu-kvm quit without save bitmaps in image(coredump or panic on host),
bitmaps in image can not be used safely anymore, and can not be removed 
also. Useless bitmaps should be removed.

Signed-off-by: Yaoxu19870920 <13466399134@163.com>
---
diff --git a/blockdev.c b/blockdev.c
index c85056a74b..58d7570932 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2837,35 +2837,31 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
     Error *local_err = NULL;
 
     bitmap = block_dirty_bitmap_lookup(node, name, &bs, errp);
-    if (!bs) {
+    if (!bitmap || !bs) {
         return;
     }
 
-    if (bitmap){
-        if (bdrv_dirty_bitmap_frozen(bitmap)) {
-            error_setg(errp,
-                       "Bitmap '%s' is currently frozen and cannot be removed",
-                       name);
-            return;
-        } else if (bdrv_dirty_bitmap_qmp_locked(bitmap)) {
-            error_setg(errp,
-                       "Bitmap '%s' is currently locked and cannot be removed",
-                       name);
-            return;
-        }
-    }
-
-    bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
-    if (local_err != NULL) {
-        error_propagate(errp, local_err);
+    if (bdrv_dirty_bitmap_frozen(bitmap)) {
+        error_setg(errp,
+                   "Bitmap '%s' is currently frozen and cannot be removed",
+                   name);
+        return;
+    } else if (bdrv_dirty_bitmap_qmp_locked(bitmap)) {
+        error_setg(errp,
+                   "Bitmap '%s' is currently locked and cannot be removed",
+                   name);
         return;
     }
 
-    if (bitmap){
-        bdrv_release_dirty_bitmap(bs, bitmap);
+    if (bdrv_dirty_bitmap_get_persistance(bitmap)) {
+        bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
+        if (local_err != NULL) {
+            error_propagate(errp, local_err);
+            return;
+        }
     }
 
-    *errp = NULL;
+    bdrv_release_dirty_bitmap(bs, bitmap);
 }
 
 /**