fdo#62994 reportbuilder survive empty formula

Change-Id: I1da053871d107730ad9a135deb48313d8a877d89
diff --git a/reportbuilder/java/org/libreoffice/report/pentaho/layoutprocessor/FormattedTextLayoutController.java b/reportbuilder/java/org/libreoffice/report/pentaho/layoutprocessor/FormattedTextLayoutController.java
index 5bda08b..1841122 100644
--- a/reportbuilder/java/org/libreoffice/report/pentaho/layoutprocessor/FormattedTextLayoutController.java
+++ b/reportbuilder/java/org/libreoffice/report/pentaho/layoutprocessor/FormattedTextLayoutController.java
@@ -84,6 +84,8 @@ public class FormattedTextLayoutController
        {
            final FormattedTextElement element = (FormattedTextElement) getNode();
            final FormulaExpression formulaExpression = element.getValueExpression();
            if (formulaExpression.getFormulaExpression() == null)
                return false;
            final Formula formula = formulaExpression.getCompiledFormula();
            final LValue lValue = formula.getRootReference();
            return FormatValueUtility.isReferenceChanged(this, lValue);