(1) -> matrix([[0,0],[0,0]]) ^ 0.1

   (1)  0.0
                                                                  Type: Float

(2) -> matrix([[0,0],[0,0]]) ^ x
         x
   (2)  0
Type: Expression Integer

but (fortunately)

(3) matrix([[0,0],[0,1]]) ^ 0.1
   There are 4 exposed and 0 unexposed library operations named ^
      having 2 argument(s) but none was determined to be applicable.
      Use HyperDoc Browse, or issue
                                )display op ^
      to learn more about the available operations. Perhaps
      package-calling the operation or using coercions on the arguments
      will allow you to apply the operation.

   Cannot find a definition or applicable library operation named ^
      with argument type(s)
                               Matrix Integer
                                    Float

      Perhaps you should use "@" to indicate the required return type,
      or "$" to specify which version of the function you need.

So it seems to happen only with the zero matrix.