Bugfix: (EliuFlorez) Work item GH-279 - Fatal error: Call to a member…

… function cellExists() line: 3327 in calculation.php if referenced worksheet doesn't exist

changelog.txt

@@ -44,6 +44,7 @@ Fixed in develop branch for release v1.8.0:
 - Bugfix:   (MBaker)          Work Item GH-193  - Fix to empty worksheet garbage collection when using cell caching
 - Bugfix:   (Jazzo)           Work Item GH-248  - Excel2007 does not correctly mark rows as hidden
 - Bugfix:   (Roy Shahbazian)  Work Item GH-299  - Fixed typo in Chart/Layout set/getYMode()
+- Bugfix:   (EliuFlorez)      Work item GH-279  - Fatal error: Call to a member function cellExists() line: 3327 in calculation.php if referenced worksheet doesn't exist
 - Feature:  (amerov)                            - Implementation of the Excel HLOOKUP() function
 - Feature:  (MBaker)                            - Added "Quote Prefix" to style settings (Excel2007 Reader and Writer only)
 - Feature:  (MBaker)                            - Added Horizontal FILL alignment for Excel5 and Excel2007 Readers/Writers, and Horizontal DISTRIBUTED alignment for Excel2007 Reader/Writer