Fix DailyLimits passing undefined values into SpinBox

If the type says it's a number, we should ensure it's a number :-)

This also fixes fields being empty when they contain a 0 value.

ts/components/SpinBox.svelte

@@ -23,7 +23,7 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
     }
 
     let stringValue: string;
-    $: if (value) stringValue = value.toFixed(decimalPlaces(step));
+    $: stringValue = value.toFixed(decimalPlaces(step));
 
     function update(this: HTMLInputElement): void {
         const newValue = parseFloat(this.value);

ts/deck-options/DailyLimits.svelte

@@ -126,8 +126,8 @@
             : [],
     );
 
-    let newValue: number;
-    let reviewsValue: number;
+    let newValue = 0;
+    let reviewsValue = 0;
 
     const settings = {
         newLimit: {