Fix an assert() failure that could occur if the internal sqlite3_rename_parent() SQL scalar function was invoked directly.

FossilOrigin-Name: 36e515261825be60ffdc73d13340d77cf377e8e1

src/alter.c

@@ -126,6 +126,7 @@ static void renameParentFunc(
         n = sqlite3GetToken(z, &token);
       }while( token==TK_SPACE );
 
+      if( token==TK_ILLEGAL ) break;
       zParent = sqlite3DbStrNDup(db, (const char *)z, n);
       if( zParent==0 ) break;
       sqlite3Dequote(zParent);