Fix foorterFormatter return 0 bug

CHANGELOG.md

@@ -7,9 +7,10 @@ ChangeLog
 - **Update(js):** Fixed showFullscreen cannot work bug.
 - **Update(js):** Redefined customSearch option.
 - **Update(js):** Fixed show footer cannot work bug.
+- **Update(js):** Updated the parameter of `footerStyle`.
+- **Update(js):** Added classes supported for `footerStyle`.
 - **Update(js):** Fixed IE11 transform bug.
 - **Update(js):** Removed beginning and end whitespace from td.
-- **Update(js):** Updated the parameter of `footerStyle` and supported css/classes.
 - **Update(export extension):** Fixed export selected bug.
 
 ### 1.13.4

src/bootstrap-table.js

@@ -2319,7 +2319,7 @@
         html.push('<th', class_, Utils.sprintf(' style="%s"', falign + valign + csses.concat().join('; ')), '>')
         html.push('<div class="th-inner">')
 
-        html.push(Utils.calculateObjectValue(column, column.footerFormatter, [data], '') || '')
+        html.push(Utils.calculateObjectValue(column, column.footerFormatter, [data], ''))
 
         html.push('</div>')
         html.push('<div class="fht-cell"></div>')