fix checking for correct formatter in durationDecimal (#5943)

phpstan.neon

@@ -3645,11 +3645,6 @@ parameters:
             count: 1
             path: src/Utils/JavascriptFormatConverter.php
 
-        -
-            message: "#^Cannot call method format\\(\\) on NumberFormatter\\|null\\.$#"
-            count: 1
-            path: src/Utils/LocaleFormatter.php
-
         -
             message: "#^Cannot call method getTimestamp\\(\\) on DateTime\\|null\\.$#"
             count: 1

src/Utils/LocaleFormatter.php

@@ -75,7 +75,7 @@ final class LocaleFormatter
      */
     public function durationDecimal(Timesheet|int|string|null $duration): string
     {
-        if (null === $this->numberFormatter) {
+        if (null === $this->decimalFormatter) {
             $this->decimalFormatter = new NumberFormatter($this->locale, NumberFormatter::DECIMAL);
             $this->decimalFormatter->setAttribute(NumberFormatter::FRACTION_DIGITS, 2);
         }