added return value to add function in matrix.c

matrix.c

@@ -108,6 +108,7 @@ Matrix add(const Matrix matrix1, const Matrix matrix2)
                 outputMatrix.buffer[i-1+ outputMatrix.rows*(j-1)] = matrix1.buffer[i-1 + matrix1.rows*(j-1)] + matrix2.buffer[i-1 + matrix2.rows *(j-1)];
             }
         }
+        return outputMatrix;
     } else {
         //the matrix could not be added, since the matrix sizes are not set correct.
         Matrix m;