[b,m]=assert_checkequal(5, "a") yields an error instead of just returning the message in m.

Reported by Samuel GOUGEON (@sgougeon)

BUG DESCRIPTION:
----------------
[b, m] = assert_checkequal(5, "a") yields an error instead of just returning the error message in m.
Its code shows that this occurs in other occasions:

--> [b, m] = assert_checkequal(5, "Bkk")
at line    12 of function assert_checkequal ( SCI\modules\development_tools\macros\assert\assert_checkequal.sci line 24 )
assert_checkequal: Incompatible input arguments #1 and #2: Same types expected.

--> [b, m] = assert_checkequal(5, [3 4])
at line    34 of function assert_checkequal ( SCI\modules\development_tools\macros\assert\assert_checkequal.sci line 46 )
assert_checkequal: Incompatible input arguments #1 and #2: Same sizes expected.

--> [b, m] = assert_checkequal(1, 1+0*%i)
at line    43 of function assert_checkequal ( SCI\modules\development_tools\macros\assert\assert_checkequal.sci line 55 )
assert_checkequal: Computed is real, but expected is complex.


ERROR LOG:
----------


HOW TO REPRODUCE THE BUG:
-------------------------
[b, m] = assert_checkequal(5, "Bkk");
[b, m] = assert_checkequal(5, [3 4]);
[b, m] = assert_checkequal(1, 1+0*%i);