[FIX] owkaplanmeier: cast to a float before fitting the Kaplan-Meier curve.

[JakaKokosar]

Issue

Error occures when this line is called. When dealing with meta attributes values of numpy array are of type 'object' instead of float (see images below).

In [26]: test = np.asarray([1]).squeeze()
In [27]: pd.to_numeric(test)
Out[27]: array(1)
In [28]: test = test.astype(object)
In [29]: pd.to_numeric(test)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-29-04b5b66c3566> in <module>
----> 1 pd.to_numeric(test)
~/.pyenv/versions/3.8.6/envs/orange/lib/python3.8/site-packages/pandas/core/tools/numeric.py in to_numeric(arg, errors, downcast)
    147         coerce_numeric = errors not in ("ignore", "raise")
    148         try:
--> 149             values = lib.maybe_convert_numeric(
    150                 values, set(), coerce_numeric=coerce_numeric
    151             )
pandas/_libs/lib.pyx in pandas._libs.lib.maybe_convert_numeric()
ValueError: Buffer has wrong number of dimensions (expected 1, got 0)

1.)

2.)

Description of changes

Includes

• [X] Code changes
• [ ] Tests
• [ ] Documentation

[codecov-io]

Codecov Report

Merging #10 (6d20119) into master (1fe2cd3) will increase coverage by 0.08%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #10      +/-   ##
==========================================
+ Coverage   93.73%   93.82%   +0.08%     
==========================================
  Files           2        2              
  Lines         351      356       +5     
==========================================
+ Hits          329      334       +5     
  Misses         22       22              

Impacted Files	Coverage Δ
...contrib/survival_analysis/widgets/owkaplanmeier.py	93.75% <100.00%> (+0.09%)	:arrow_up:

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