Workaround a cmake bug that was only visible on a newly installed Philip's machine.

CMake 2.8.4 crashed on this line
 IF(something AND IS_DIRECTORY(something_else))
when both  "something" and "something_else" were empty.

Changing the line slightly (using cascading "IF" instead)  solved the crash.

win/packaging/create_msi.cmake.in

@@ -304,10 +304,12 @@ ENDFUNCTION()
 
 FUNCTION(TRAVERSE_DIRECTORIES dir topdir file prefix)
   FILE(RELATIVE_PATH rel ${topdir} ${dir})
-  IF(rel AND IS_DIRECTORY "${f}")
-    MAKE_WIX_IDENTIFIER("${rel}" id)
-    GET_FILENAME_COMPONENT(name ${dir} NAME)
-    FILE(APPEND ${file} "${prefix}<Directory Id='D.${id}' Name='${name}'>\n")
+  IF(rel)
+    IF (IS_DIRECTORY "${f}")
+      MAKE_WIX_IDENTIFIER("${rel}" id)
+      GET_FILENAME_COMPONENT(name ${dir} NAME)
+      FILE(APPEND ${file} "${prefix}<Directory Id='D.${id}' Name='${name}'>\n")
+    ENDIF()
   ENDIF()
   FILE(GLOB all_files ${dir}/*)
     FOREACH(f ${all_files})
@@ -315,8 +317,10 @@ FUNCTION(TRAVERSE_DIRECTORIES dir topdir file prefix)
       TRAVERSE_DIRECTORIES(${f} ${topdir} ${file} "${prefix}  ")
     ENDIF()
   ENDFOREACH()
-  IF(rel AND IS_DIRECTORY "${f}")
-    FILE(APPEND ${file} "${prefix}</Directory>\n")
+  IF(rel)
+    IF(IS_DIRECTORY "${f}")
+      FILE(APPEND ${file} "${prefix}</Directory>\n")
+    ENDIF()
   ENDIF()
 ENDFUNCTION()