Fix another regression caused by #609.

[drgrice1]

If a problem sets the answer to be a formula with an assigment, (something like Formula("x = 5") then all answers are counted
incorrect and a warning is displayed that the evaluated answer is not an answer hash. This worked prior to #609. The cause of this was the removal of a line that should not have been removed that converts the other answer being compared to to a Formula if it is not already.

Note that the original issue that was attempted to be fixed by #609 still is fixed with this change.

This fixes issue #644 that I just submitted about this.

Attached are minimal working examples for the original issue as well as for this one.
FormulaAssignment.pg.txt
ParserAssignmentMWE.pg.txt
See issue #607 for details on how to test ParserAssignmentMWE.pg, and issue #644 for details on testing FormulaAssignment.pg.

Note that this is definitely a hotfix. This certainly brings in to question that #609 should have been a hotfix, considering that this is something that has been this way since 2008.

[somiaj]

I can confirm this fix works. I just ran across a very similar issue where if the answer was Compute("y=5+2x") and the student entered in just y=5 as their answer it produced the error described in #644. The grader would would still accept the correct answer (and also not error out if any variable was used, like y=3t, but be marked incorrect).

[drgrice1]

@somiaj: I can confirm the behavior you describe with the ParserAssignmentMWE.pg problem that I attached above. If you enter y=5 it gives the evaluated answer is not an answer hash. This pull request fixes that also.

[pstaabp]

Having trouble getting my main branch running well, but the develop branch looks good and noticed that this does restore the line that was deleted.