BUG#29445 - match ... against () never returns

Part 1:
Do not perform index search for a plus-word with truncation operator
in case there are other plus-words in expression.

Specifically this optimization was enforced for expression like
"+word1 +word2*", but wasn't enforced for expression like
"+word1 word2*".

mysql-test/r/fulltext.result

@@ -480,3 +480,9 @@ CREATE TABLE t1(a VARCHAR(2) CHARACTER SET big5 COLLATE big5_chinese_ci,
 FULLTEXT(a));
 INSERT INTO t1 VALUES(0xA3C2);
 DROP TABLE t1;
+CREATE TABLE t1(a VARCHAR(20), FULLTEXT(a));
+INSERT INTO t1 VALUES('Offside'),('City Of God');
+SELECT a FROM t1 WHERE MATCH a AGAINST ('+city of*' IN BOOLEAN MODE);
+a
+City Of God
+DROP TABLE t1;

mysql-test/t/fulltext.test

@@ -408,4 +408,12 @@ FULLTEXT(a));
 INSERT INTO t1 VALUES(0xA3C2);
 DROP TABLE t1;
 
+#
+# BUG#29445 - match ... against () never returns
+#
+CREATE TABLE t1(a VARCHAR(20), FULLTEXT(a));
+INSERT INTO t1 VALUES('Offside'),('City Of God');
+SELECT a FROM t1 WHERE MATCH a AGAINST ('+city of*' IN BOOLEAN MODE);
+DROP TABLE t1;
+
 # End of 4.1 tests

storage/myisam/ft_boolean_search.c

@@ -474,7 +474,8 @@ static void _ftb_init_index_search(FT_INFO *ftb)
            ftbe->up->flags|= FTB_FLAG_TRUNC, ftbe=ftbe->up)
       {
         if (ftbe->flags & FTB_FLAG_NO ||                     /* 2 */
-             ftbe->up->ythresh - ftbe->up->yweaks >1)        /* 1 */
+            ftbe->up->ythresh - ftbe->up->yweaks >
+            test(ftbe->flags & FTB_FLAG_YES))                /* 1 */
         {
           FTB_EXPR *top_ftbe=ftbe->up;
           ftbw->docid[0]=HA_OFFSET_ERROR;