Add missing dot-product dimension check.

Fix #776

src/base/blas.rs

@@ -289,6 +289,13 @@ where
             rhs.shape(),
         );
 
+        assert!(
+            self.ncols() == rhs.ncols(),
+            "Dot product dimensions mismatch for shapes {:?} and {:?}: left cols != right cols.",
+            self.shape(),
+            rhs.shape(),
+        );
+
         // So we do some special cases for common fixed-size vectors of dimension lower than 8
         // because the `for` loop below won't be very efficient on those.
         if (R::is::<U2>() || R2::is::<U2>()) && (C::is::<U1>() || C2::is::<U1>()) {