Make index handling for clusters more explicit

We rely on the fact that vertices of clusters represented
in igraph objects have consecutive indices starting from 1,
but this is currently only true because of a side effeft (column
names get lost when the adjacency matrix is transposed in
performAnalysis). Since consecutive labels are a) assumed by
the rest of the code and b) required for some graph operations,
ensure that the property is actively enforced.

Signed-off-by: Wolfgang Mauerer <wolfgang.mauerer@siemens.com>
Fix some formal issues in person.r

Correct faulty indentation, and remove a typo in a comment.

Signed-off-by: Wolfgang Mauerer <wolfgang.mauerer@siemens.com>
Do not overwrite commit date in complexity analysis

The commit date is taken from the list of commits, but later
on incidentally overwritten with the date from the understand
analysis. However, understand can fail in some inputs, which
leads to good dates being transformed into empty dates, causing
SQL problems in turn later. Fix this by not setting a potentially
bogus date at all.

Signed-off-by: Wolfgang Mauerer <wolfgang.mauerer@siemens.com>
Fix handling invalid understand results

If understand does not produce results for one reason
or another, parse.understand() returns NULL. While the
subset selection on a NULL object succeeds, the test
for the number of columns does not -- it leads to a crash
instead of skipping this result set. Properly check
for invalid results by using a check for NULL, thus.

Signed-off-by: Wolfgang Mauerer <wolfgang.mauerer@siemens.com>