do not crash on myrg_rprev/myrg_rnext if no current table

(as when previous myrg_rkey failed, e.g. found nothing)

myisammrg/myrg_delete.c

@@ -23,8 +23,7 @@ MYRG_INFO *info,
 const byte *record)
 {
   if (!info->current_table)
-  {
-    return(my_errno=HA_ERR_NO_ACTIVE_RECORD);
-  }
+    return my_errno=HA_ERR_NO_ACTIVE_RECORD ;
+
   return mi_delete(info->current_table->table,record);
 }

myisammrg/myrg_locking.c

@@ -20,9 +20,7 @@
 
 #include "myrg_def.h"
 
-int myrg_lock_database(
-MYRG_INFO *info,
-int lock_type)
+int myrg_lock_database(MYRG_INFO *info, int lock_type)
 {
   int error,new_error;
   MYRG_TABLE *file;

myisammrg/myrg_rnext.c

@@ -25,6 +25,9 @@ int myrg_rnext(MYRG_INFO *info, byte *buf, int inx)
   int err;
   MI_INFO *mi;
 
+  if (!info->current_table)
+    return HA_ERR_KEY_NOT_FOUND;
+
   /* at first, do rnext for the table found before */
   if ((err=mi_rnext(info->current_table->table,NULL,inx)))
   {

myisammrg/myrg_rprev.c

@@ -25,8 +25,8 @@ int myrg_rprev(MYRG_INFO *info, byte *buf, int inx)
   int err;
   MI_INFO *mi;
 
-  if (!info || !info->current_table)
-    return HA_ERR_UNSUPPORTED;
+  if (!info->current_table)
+    return HA_ERR_KEY_NOT_FOUND;
 
   /* at first, do rprev for the table found before */
   if ((err=mi_rprev(info->current_table->table,NULL,inx)))

myisammrg/myrg_rrnd.c

@@ -24,7 +24,7 @@
 static MYRG_TABLE *find_table(MYRG_TABLE *start,MYRG_TABLE *end,ulonglong pos);
 
 /*
-  	If filepos == HA_OFFSET_ERROR, read next
+	If filepos == HA_OFFSET_ERROR, read next
 	Returns same as mi_rrnd:
 	   0 = Ok.
 	   HA_ERR_RECORD_DELETED = Record is deleted.

myisammrg/myrg_rsame.c

@@ -19,12 +19,10 @@
 int myrg_rsame(MYRG_INFO *info,byte *record,int inx)
 {
   if (inx)					/* not yet used, should be 0 */
-  {
-    return(my_errno=HA_ERR_WRONG_INDEX);
-  }
+    return my_errno=HA_ERR_WRONG_INDEX;
+
   if (!info->current_table)
-  {
-    return(my_errno=HA_ERR_NO_ACTIVE_RECORD);
-  }
+    return my_errno=HA_ERR_NO_ACTIVE_RECORD;
+
   return mi_rsame(info->current_table->table,record,inx);
 }

myisammrg/myrg_update.c

@@ -21,6 +21,7 @@
 int myrg_update(register MYRG_INFO *info,const byte *oldrec, byte *newrec)
 {
   if (!info->current_table)
-    return(my_errno=HA_ERR_NO_ACTIVE_RECORD);
+    return my_errno=HA_ERR_NO_ACTIVE_RECORD;
+
   return mi_update(info->current_table->table,oldrec,newrec);
 }

myisammrg/myrg_write.c

@@ -26,5 +26,5 @@ int myrg_write(register MYRG_INFO *info, byte *rec)
   else if (info->merge_insert_method == MERGE_INSERT_TO_LAST)
     return mi_write(info->end_table[-1].table,rec);
   else /* unsupported insertion method */
-    return (my_errno=HA_ERR_WRONG_COMMAND); 
+    return my_errno=HA_ERR_WRONG_COMMAND;
 }