change some usages that assumed null from readfully

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@572329 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/filters/ClassConstants.java

@@ -101,7 +101,7 @@ public final class ClassConstants
             }
         } else {
             final String clazz = readFully();
-            if (clazz == null) {
+            if (clazz == null && clazz.length() != 0) {
                 ch = -1;
             } else {
                 final byte[] bytes = clazz.getBytes("ISO-8859-1");

src/main/org/apache/tools/ant/filters/ExpandProperties.java

@@ -84,7 +84,7 @@ public final class ExpandProperties
             }
         } else {
             queuedData = readFully();
-            if (queuedData == null) {
+            if (queuedData.length() == 0) {
                 ch = -1;
             } else {
                 Project project = getProject();

src/main/org/apache/tools/ant/taskdefs/LoadProperties.java

@@ -164,7 +164,7 @@ public class LoadProperties extends Task {
 
             String text = crh.readFully(instream);
 
-            if (text != null) {
+            if (text != null && text.length() != 0) {
                 if (!text.endsWith("\n")) {
                     text = text + "\n";
                 }