The following gnuplot code stopped working after recent commits adding
support of remote files:

#+CALL: stress-strain[:file stress-displ-RD-11.png](A=0.87, alpha=38.0, beta=7.0, inp="p11 DC.txt", tbl="stress-displ-RD-11.txt")

Note that the code assigns several numerical variables. ob-gnuplot from
master throws error when checking (file-remote-p ...).

The fix is attached.

Best,
Ihor