Cleared also medianFirstName information from factor table once info from a block is cleared

Author: ArnauPrat

src/main/java/ldbc/snb/datagen/util/FactorTable.java

@@ -294,6 +294,7 @@ public void writePersonFactors(OutputStream writer ) {
                 }
             }
             personCounts_.clear();
+            medianFirstName_.clear();
         } catch (IOException e) {
             System.err.println("Unable to write parameter counts");
             System.err.println(e.getMessage());