fix crashing if input is empty

src/zmat.cpp

@@ -101,7 +101,10 @@ void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]){
 	       unsigned char *outputbuf=NULL;
 	       size_t outputsize=0;
 	       unsigned char * inputstr=(mxIsChar(prhs[0])? (unsigned char *)mxArrayToString(prhs[0]) : (unsigned char *)mxGetData(prhs[0]));
-    	       int errcode=zmat_run(inputsize, inputstr, &outputsize, &outputbuf, zipid, &ret, iscompress);
+    	       int errcode=0;
+	       if(inputsize>0)
+	           errcode=zmat_run(inputsize, inputstr, &outputsize, &outputbuf, zipid, &ret, iscompress);
+
                if(errcode<0){
 	           if(outputbuf)
 		       free(outputbuf);

zmat.m

@@ -91,17 +91,7 @@
     zipmethod=varargin{3};
 end
 
-if(~isempty(input))
-    [varargout{1:nargout}]=zipmat(input,iscompress,zipmethod);
-else
-    varargout{1}='';
-    if(nargout>1)
-        varargout{2}=struct('type',class(varargin{1}),'size',0,...
-            'byte',length(typecast(cast(1,class(input)),'uint8')),...
-            'method',zipmethod,'status',0,'level',iscompress);
-
-    end
-end
+[varargout{1:max(1,nargout)}]=zipmat(input,iscompress,zipmethod);
 
 if(exist('inputinfo','var') && isfield(inputinfo,'type'))
         varargout{1}=typecast(varargout{1},inputinfo.type);