Add null guard for querySelector and fix days using raw input value

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/DurationInput.vue

@@ -216,7 +216,7 @@ function onChange(event) {
   tUnits.value[dsp].val = decoratedInputValue;
   switch (dsp) {
     case "d":
-      days.value = baseInputValue;
+      days.value = decoratedInputValue;
       break;
     case "h":
       hours.value = decoratedInputValue;
@@ -297,7 +297,7 @@ function incrementPreviousUnit(input) {
     const prevUnit = document.querySelector(
       `input[data-index="${parseInt(input.dataset.index) - 1}"]`,
     );
-    actionUpDown(prevUnit, true);
+    if (prevUnit) actionUpDown(prevUnit, true);
   }
 }