Handle cycle with mucus on first cycle day

lib/sympto/index.js

@@ -16,9 +16,15 @@ export default function getSymptoThermalStatus({ cycle, previousCycle, earlierCy
   if (previousCycle) {
     const statusForLast = getSymptoThermalStatus({ cycle: previousCycle })
     if (statusForLast.temperatureShift) {
-      status.phases.preOvulatory = getPreOvulatoryPhase(cycle, [previousCycle, ...earlierCycles])
-      if (status.phases.preOvulatory.cycleDays.length === cycle.length) {
-        return status
+      const preOvuPhase = getPreOvulatoryPhase(
+        cycle,
+        [previousCycle, ...earlierCycles]
+      )
+      if (preOvuPhase) {
+        status.phases.preOvulatory = preOvuPhase
+        if (status.phases.preOvulatory.cycleDays.length === cycle.length) {
+          return status
+        }
       }
     }
   }

lib/sympto/pre-ovulatory.js

@@ -13,6 +13,9 @@ export default function(cycle, previousCycles) {
     return d.date <= preOvuEndDate
   })
   const preOvulatoryDays = getDaysUntilFertileMucus(maybePreOvuDays)
+  // if mucus occurs on the 1st cycle day, there is no pre-ovu phase
+  if (!preOvulatoryDays.length) return null
+
   let endDate
   if (preOvulatoryDays.length === maybePreOvuDays.length) {
     endDate = preOvuEndDate