Fix NPE when previous technical debt was null

sonar-core/src/main/java/org/sonar/core/issue/IssueUpdater.java

@@ -204,7 +204,7 @@ public class IssueUpdater implements BatchComponent, ServerComponent {
     TechnicalDebt oldValue = issue.technicalDebt();
     if (!Objects.equal(value, oldValue)) {
       issue.setTechnicalDebt(value);
-      issue.setFieldChange(context, TECHNICAL_DEBT, oldValue.toLong(), value.toLong());
+      issue.setFieldChange(context, TECHNICAL_DEBT, oldValue != null ? oldValue.toLong() : oldValue, value != null ? value.toLong() : null);
       issue.setUpdateDate(context.date());
       issue.setChanged(true);
       return true;

sonar-core/src/test/java/org/sonar/core/issue/IssueUpdaterTest.java

@@ -378,6 +378,33 @@ public class IssueUpdaterTest {
     assertThat(diff.newValue()).isEqualTo(TechnicalDebt.of(15, 0, 0).toLong());
   }
 
+  @Test
+  public void set_past_technical_debt_without_previous_value() throws Exception {
+    issue.setTechnicalDebt(TechnicalDebt.of(15, 0, 0));
+    boolean updated = updater.setPastTechnicalDebt(issue, null, context);
+    assertThat(updated).isTrue();
+    assertThat(issue.technicalDebt()).isEqualTo(TechnicalDebt.of(15, 0, 0));
+    assertThat(issue.mustSendNotifications()).isFalse();
+
+    FieldDiffs.Diff diff = issue.currentChange().get(TECHNICAL_DEBT);
+    assertThat(diff.oldValue()).isNull();
+    assertThat(diff.newValue()).isEqualTo(TechnicalDebt.of(15, 0, 0).toLong());
+  }
+
+  @Test
+  public void set_past_technical_debt_with_null_new_value() throws Exception {
+    issue.setTechnicalDebt(null);
+    TechnicalDebt previousDebt = TechnicalDebt.of(10, 0, 0);
+    boolean updated = updater.setPastTechnicalDebt(issue, previousDebt, context);
+    assertThat(updated).isTrue();
+    assertThat(issue.technicalDebt()).isNull();
+    assertThat(issue.mustSendNotifications()).isFalse();
+
+    FieldDiffs.Diff diff = issue.currentChange().get(TECHNICAL_DEBT);
+    assertThat(diff.oldValue()).isEqualTo(TechnicalDebt.of(10, 0, 0).toLong());
+    assertThat(diff.newValue()).isNull();
+  }
+
   @Test
   public void set_message() throws Exception {
     boolean updated = updater.setMessage(issue, "the message", context);