FOP-2341: Infinite loop when smaller used with a zero length font-size

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@1568925 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/fop/fo/properties/FontSizePropertyMaker.java

@@ -105,6 +105,9 @@ public class FontSizePropertyMaker
             // than the last caculated step
             lastStepFontSize = nextStepFontSize;
             nextStepFontSize = (int)Math.round(lastStepFontSize * scale);
+            if (nextStepFontSize == lastStepFontSize) {
+                break;
+            }
         }
         // baseFontSize is between last and next step font size
         // Return the step value closer to the baseFontSize