Ensure backward compatible testing of types (#1266)

- Use "type(0)" instead of "v:t_number"
- Use "==" instead of "==#" since we are comparing numbers
- Make use of the "+=" operator
- Update the "CHANGELOG.md" file

The only real issue here is that we should prefer "type(0)" over the
special variable.  I run into this problem enough on older systems
that it frustrates me.  Let's have it fixed!

CHANGELOG.md

@@ -5,7 +5,8 @@
         - **.PATCH**: Pull Request Title (PR Author) [PR Number](Link to PR)
 -->
 #### 6.10
-- **.14**:  Replace trim() with a version-compatible alternative. (PhilRunninger) [#1265](https://github.com/preservim/nerdtree/pull/1265)
+- **.15**: Ensure backward compatible testing of types. (lifecrisis) [#1266](https://github.com/preservim/nerdtree/pull/1266)
+- **.14**: Replace trim() with a version-compatible alternative. (PhilRunninger) [#1265](https://github.com/preservim/nerdtree/pull/1265)
 - **.13**: Change highlighting of bookmarks in the tree. (PhilRunninger) [#1261](https://github.com/preservim/nerdtree/pull/1261)
 - **.12**: Answer the question about accessing files over scp or ftp. (PhilRunninger) [#1259](https://github.com/preservim/nerdtree/pull/1259)
 - **.11**: Trim filenames created via the fs_menu (elanorigby) [#1243](https://github.com/preservim/nerdtree/pull/1243)

autoload/nerdtree.vim

@@ -112,18 +112,18 @@ function! nerdtree#compareNodePaths(p1, p2) abort
         " Compare chunks upto common length.
         " If chunks have different type, the one which has
         " integer type is the lesser.
-        if type(sortKey1[i]) ==# type(sortKey2[i])
+        if type(sortKey1[i]) == type(sortKey2[i])
             if sortKey1[i] <# sortKey2[i]
                 return - 1
             elseif sortKey1[i] ># sortKey2[i]
                 return 1
             endif
-        elseif type(sortKey1[i]) ==# v:t_number
+        elseif type(sortKey1[i]) == type(0)
             return -1
-        elseif type(sortKey2[i]) ==# v:t_number
+        elseif type(sortKey2[i]) == type(0)
             return 1
         endif
-        let i = i + 1
+        let i += 1
     endwhile
 
     " Keys are identical upto common length.