Allow for disabling reports by email.

This diff simply adds one line:

`if [ ! -z "$reportemail" ]; then` and then it indents the if block and adds a
final `fi`.

This check used to be there, without it, its not possible to disable report
mails, which might be something desirable if you are getting alerts through the
prometheus method.

src/backupninja.in

@@ -661,6 +661,7 @@ EOF
          let "errors +-1"
       fi
    fi
+   if [ ! -z "$reportemail" ]; then
       if [ -x "$(which mail 2>/dev/null)" ]; then
          debug "send report to $reportemail"
          hostname=`hostname`
@@ -690,7 +691,7 @@ EOF
          let "errors += 1"
       fi
    fi
-
+fi
 if [ $actions_run != 0 ]; then
    info "FINISHED: $actions_run actions run. $fatals fatal. $errors error. $warnings warning."
    if [ "$halts" != "0" ]; then