Prevent crash when tapping on Minutely on Today on the first launch.

1Weather/UI/View controllers/Forecast/Cells/ForecastCellFactory.swift

@@ -277,6 +277,9 @@ class ForecastCellFactory: CellFactory {
                 adLoggingEmoji = "✅"
                 adLoggingEmoji = "✅"
             }
             }
         default:
         default:
+            //TODO: this shouldn't happen but it does, when the user clicks on Minutely on the Today screen on first launch.
+            placementName = ""
+            timePeriodString = ""
             break
             break
         }
         }