Add alert for unsupported queries

[stilscher]

This PR contains the handling of the exception that is introduced in goblint/cil#147 (comment). It is used to distinguish between "No results found" and "Query not supported" in the syntactic analysis. In the case the Query is not supported, GobView will, with the changes of this PR display two different alert texts instead of just "No results found" in both cases. This should help to make the results of the search more transparent/understandable.

An example for a syntactic query that is not supported is finding the declaration of a function by name:
{"kind":["fun"],"target":["name","pthread_once"],"find":["decl"],"expression":"","mode":["Must"]}
on
tests/regression/00-sanity/01-assert.c

[sim642]

This seems to cause a build error now:

File "gobview/src/state/search.ml", line 13, characters 49-59:
13 |     { kind; target; find; structure; limitation; expression; mode }
                                                      ^^^^^^^^^^
Error: This expression has type 'a option
       but an expression was expected of type string

I guess it also requires some change in Goblint or CIL itself?

[stilscher]

I guess it also requires some change in Goblint or CIL itself?

Yes, this is the corresponding not yet merged PR for the changes on the Goblint side: goblint/analyzer#1092