[CMake],[release] Fix bug with dependency version handling.

Dependencies in the dune.module without a required version failed.
(cherry picked from commit 63a24c54)

Signed-off-by: Markus Blatt <markus@dr-blatt.de>

cmake/modules/DuneMacros.cmake

@@ -104,7 +104,9 @@ macro(find_dune_package module)
     string(STRIP ${DUNE_FIND_VERSION_NUMBER} DUNE_FIND_VERSION_NUMBER)
     extract_major_minor_version("${DUNE_FIND_VERSION_NUMBER}" DUNE_FIND_VERSION)
     set(DUNE_FIND_VERSION_STRING "${DUNE_FIND_VERSION_MAJOR}.${DUNE_FIND_VERSION_MINOR}.${DUNE_FIND_VERSION_REVISION}")
-      endif(DUNE_FIND_VERSION MATCHES "(>=|=|<=).*")
+  else()
+    set(DUNE_FIND_VERSION_STRING "0.0.0")
+  endif(DUNE_FIND_VERSION MATCHES "(>=|=|<=).*")
   if(NOT ${module}_FOUND)
     if(NOT (${module}_DIR OR ${module}_ROOT OR
        "${CMAKE_PREFIX_PATH}" MATCHES ".*${module}.*"))