Fix NPE in YieldResponse

src/ac/ed/lurg/yield/YieldResponse.java

@@ -75,8 +75,6 @@ public class YieldResponse {
 			
 			if (Double.isNaN(asymptoteYieldIncI) || Double.isNaN(fertParm)) {
 				LogWriter.println("Not finding a suitable extrapolating solution.  Defaulting to old style");
-				fertParm = calcParam(yMinNoI, yMidNoI, yMaxNoI, fMid);
-				yieldsExtrapolated = yields;
 			}
 			else {
 				yieldsExtrapolated = new HashMap<YieldType, Double>();
@@ -86,8 +84,11 @@ public class YieldResponse {
 				yieldsExtrapolated.put(YieldType.FERT_MAX_IRRIG_MAX, asymptoteYieldIncI+yMinI);
 			}
 		}
-		else {
+		
+		// old style, if not wanting extrapolate or data doesn't allow
+		if (yieldsExtrapolated == null) {
 			fertParm = calcParam(yMinNoI, yMidNoI, yMaxNoI, fMid);
+			yieldsExtrapolated = yields;
 		}
 		
 		return fertParm;