Removed unnecessary check when opening viewer.

****squash with unecessary check

src/matlab/+D3d/IsOpen.m

+function isOpen = IsOpen()
+    global D3dIsOpen
+
+    isOpen = false;
+    if (~isempty(D3dIsOpen))
+        isOpen = D3dIsOpen;
+    end
+end

src/matlab/+D3d/Open.m

@@ -31,9 +31,8 @@ function [varargout] = Open( im, imData, imagePath, mesagePkgStr )
     else
         EXT_MESAGE_FUNC = mesagePkgStr;
     end
-    if (isempty(D3dIsOpen))
-        D3dIsOpen = false;
-    end
+    
+    D3dIsOpen = D3d.IsOpen();
     
     %% check for missing data that we might need and load
     openedMetadata = false;