Bug #29252 Assertion 'table->file || table->file->inited == handler::NONE' failed

when index_init() or rnd_init() return an error, we still set
handler->inited to INDEX or RND in ha_index_init and ha_rnd_init.
As caller doesn't call ha_*_end() in this case, we get DBUG_ASSERT
failed.

sql/handler.h

@@ -1097,10 +1097,12 @@ public:
 
   int ha_index_init(uint idx, bool sorted)
   {
+    int result;
     DBUG_ENTER("ha_index_init");
     DBUG_ASSERT(inited==NONE);
-    inited=INDEX;
-    DBUG_RETURN(index_init(idx, sorted));
+    if (!(result= index_init(idx, sorted)))
+      inited=INDEX;
+    DBUG_RETURN(result);
   }
   int ha_index_end()
   {
@@ -1111,10 +1113,11 @@ public:
   }
   int ha_rnd_init(bool scan)
   {
+    int result;
     DBUG_ENTER("ha_rnd_init");
     DBUG_ASSERT(inited==NONE || (inited==RND && scan));
-    inited=RND;
-    DBUG_RETURN(rnd_init(scan));
+    inited= (result= rnd_init(scan)) ? NONE: RND;
+    DBUG_RETURN(result);
   }
   int ha_rnd_end()
   {