Fix find module not working when no version number was given

cmake/protobuf-config-version.cmake.in

@@ -17,11 +17,12 @@ endif()
 
 set(PACKAGE_VERSION_COMPATIBLE TRUE) #Assume true until shown otherwise
 
-if(NOT PACKAGE_FIND_VERSION_MAJOR EQUAL "@protobuf_VERSION_MAJOR@")
+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)
+  elseif(PACKAGE_FIND_VERSION VERSION_GREATER PACKAGE_VERSION)
     set(PACKAGE_VERSION_COMPATIBLE FALSE)
-elseif(PACKAGE_FIND_VERSION VERSION_EQUAL PACKAGE_VERSION)
+  elseif(PACKAGE_FIND_VERSION VERSION_EQUAL PACKAGE_VERSION)
     # Do not match prerelease versions to non-prerelease version requests.
       if(NOT "@protobuf_VERSION_PRERELEASE@" STREQUAL "" AND PACKAGE_FIND_VERSION_PRERELEASE STREQUAL "")
       message(AUTHOR_WARNING "To use this prerelease version of ${PACKAGE_FIND_NAME}, set ${PACKAGE_FIND_NAME}_FIND_VERSION_PRERELEASE to '@protobuf_VERSION_PRERELEASE@' or greater.")
@@ -32,6 +33,7 @@ elseif(PACKAGE_FIND_VERSION VERSION_EQUAL PACKAGE_VERSION)
     if(PACKAGE_FIND_VERSION_PRERELEASE STRGREATER "@protobuf_VERSION_PRERELEASE@")
       set(PACKAGE_VERSION_COMPATIBLE FALSE)
     endif()
+  endif()
 endif()
 
 # Check and save build options used to create this package