feat: remember inferred location in unifyPair

src/main/java/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java

@@ -106,7 +106,11 @@ public class UnifyPair implements IConstraintElement, ISerializableData {
 
 	public SourceLoc getLocation() {
 		if (location != null) return location;
-		else if (basePair != null) return basePair.getLocation();
+		else if (basePair != null) {
+			SourceLoc baseLocation = basePair.getLocation();
+			location = baseLocation;
+			return baseLocation;
+		}
 		return null;
 	}