NPE when comparing 2 empty matrices

[alexott]

As part of investigation for incanter's bug #149 I've found that comparison of 2 empty matrices causes NPE in the jBlas:

 user> (= (matrix []) (matrix []))
 NullPointerException   org.jblas.JavaBlas.rcopy (JavaBlas.java:80)

Following change in Matrix deftype in clatrix fixes comparison of matrices, but it still fails for comparison of empty vector and empty matrix, etc.

 (matrix? that) (if (and (= (count this) 0) (= (count that) 0))
                  true
                  (.equals (.me this) (.me that)))

I'm not sure - this is jBlas's issue or clatrix's