fix possible crash in headlinesfragment.refresh if invoked when fragment

is not yet initialized

AndroidManifest.xml

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.fox.ttrss"
-    android:versionCode="184"
-    android:versionName="1.8.4" >
+    android:versionCode="185"
+    android:versionName="1.8.5" >
 
     <uses-sdk
         android:minSdkVersion="8"

src/org/fox/ttrss/FeedsFragment.java

@@ -282,7 +282,6 @@ public class FeedsFragment extends Fragment implements OnItemClickListener, OnSh
 	@SuppressWarnings({ "unchecked", "serial" })
 	public void refresh(boolean background) {
 		//FeedCategory cat = m_onlineServices.getActiveCategory();
-
 		m_activity.setProgressBarVisibility(true);
 		
 		final int catId = (m_activeCategory != null) ? m_activeCategory.id : -4;

src/org/fox/ttrss/HeadlinesFragment.java

@@ -362,7 +362,7 @@ public class HeadlinesFragment extends Fragment implements OnItemClickListener,
 
 	@SuppressWarnings({ "unchecked", "serial" })
 	public void refresh(boolean append) {
-		if (m_activity != null) {
+		if (m_activity != null && m_feed != null) {
 			m_refreshInProgress = true;
 
 			m_activity.setProgressBarVisibility(true);