Index: /trunk/src/VBox/Main/src-client/GuestSessionImplTasks.cpp
===================================================================
--- /trunk/src/VBox/Main/src-client/GuestSessionImplTasks.cpp	(revision 83605)
+++ /trunk/src/VBox/Main/src-client/GuestSessionImplTasks.cpp	(revision 83606)
@@ -1406,4 +1406,7 @@
      */
 
+    if (mDest.isEmpty())
+        return setProgressErrorMsg(VBOX_E_IPRT_ERROR, Utf8StrFmt(GuestSession::tr("Destination must not be empty")));
+
     GuestSessionFsSourceSet::iterator itSrc = mSources.begin();
     while (itSrc != mSources.end())
@@ -1413,4 +1416,10 @@
 
         bool    fFollowSymlinks;
+
+        if (strSrc.isEmpty())
+        {
+            strErrorInfo = Utf8StrFmt(GuestSession::tr("Source entry must not be empty"));
+            break;
+        }
 
         if (itSrc->enmType == FsObjType_Directory)
@@ -1654,4 +1663,7 @@
      */
 
+    if (mDest.isEmpty())
+        return setProgressErrorMsg(VBOX_E_IPRT_ERROR, Utf8StrFmt(GuestSession::tr("Destination must not be empty")));
+
     GuestSessionFsSourceSet::iterator itSrc = mSources.begin();
     while (itSrc != mSources.end())
@@ -1661,4 +1673,10 @@
 
         LogFlowFunc(("Source: strSrc=%s, strDst=%s\n", strSrc.c_str(), strDst.c_str()));
+
+        if (strSrc.isEmpty())
+        {
+            strErrorInfo = Utf8StrFmt(GuestSession::tr("Source entry must not be empty"));
+            break;
+        }
 
         RTFSOBJINFO srcFsObjInfo;