combining IF with Concatenate to get desired result with a "." between and no spaces

Hi I have Microsoft Office Professional 2013.

I'm using instructions from 2014 to add a formula to a spreadsheet to combine task and subtask into one column. The formula as written returns error #NAME?.

G Col.      H Col.          I Added column to combine 1st and 2nd.
Task Number Subtask Number  TaskSubtask Number
                            (desired result)
1                           1.0
1            1              1.1
1            2              1.2

there are 2624 rows.

most columns in the subtask number are blank. Some have a subtask number.

Here is the formula previously used:

=if(H2=””,concatenate(G2,”.0”),concatenate(G2,”.”,H2))

When I try to use the check formula, and change concatenate to concat the only error is in the first part if(H2="",

I've looked all over, Can you help me? Thanks!