time_zone_manager: Don't loop on zero

Avoid an infinite loop, trying to accumulate a value with zero.

src/core/hle/service/time/time_zone_manager.cpp

@@ -142,6 +142,9 @@ static constexpr bool GetInteger(const char* name, int& offset, int& value, int
     if (!IsDigit(temp)) {
         return {};
     }
+    if (temp == '0') {
+        return {};
+    }
     do {
         value = value * 10 + (temp - '0');
         if (value > max) {