Fix find module not working when no version number was given

cmake/protobuf-config-version.cmake.in

@@ -17,6 +17,7 @@ endif()
 
 set(PACKAGE_VERSION_COMPATIBLE TRUE) #Assume true until shown otherwise
 
+if(PACKAGE_FIND_VERSION) #Only perform version checks if one is given
   if(NOT PACKAGE_FIND_VERSION_MAJOR EQUAL "@protobuf_VERSION_MAJOR@")
     set(PACKAGE_VERSION_COMPATIBLE FALSE)
   elseif(PACKAGE_FIND_VERSION VERSION_GREATER PACKAGE_VERSION)
@@ -33,6 +34,7 @@ elseif(PACKAGE_FIND_VERSION VERSION_EQUAL PACKAGE_VERSION)
       set(PACKAGE_VERSION_COMPATIBLE FALSE)
     endif()
   endif()
+endif()
 
 # Check and save build options used to create this package
 macro(_check_and_save_build_option OPTION VALUE)