eval: Silence PVS/V547: E882 may be triggered

I failed to deduce why analyzer thinks E882 may not be triggered, though 
conditions for triggering it are strange: it would trigger E882 only in the 
single case “function returned non-number”. Cases “function thrown exception”, 
or “built-in sorter encountered error” will neither yield E882 nor stop 
sort()/uniq().

Note though that searching test code revealed that neither E702 nor E882 are not 
tested anywhere.

test/functional/eval/uniq_spec.lua

@@ -0,0 +1,34 @@
+local helpers = require('test.functional.helpers')(after_each)
+
+local eq = helpers.eq
+local NIL = helpers.NIL
+local eval = helpers.eval
+local clear = helpers.clear
+local meths = helpers.meths
+local funcs = helpers.funcs
+local command = helpers.command
+local exc_exec = helpers.exc_exec
+local redir_exec = helpers.redir_exec
+
+before_each(clear)
+
+describe('uniq()', function()
+  it('errors out when processing special values', function()
+    eq('Vim(call):E907: Using a special value as a Float',
+       exc_exec('call uniq([v:true, v:false], "f")'))
+  end)
+
+  it('can yield E882 and stop filtering after that', function()
+    command([[
+      function Cmp(a, b)
+        if type(a:a) == type([]) || type(a:b) == type([])
+          return []
+        endif
+        return (a:a > a:b) - (a:a < a:b)
+      endfunction
+    ]])
+    eq('\nE745: Using a List as a Number\nE882: Uniq compare function failed',
+       redir_exec('let fl = uniq([0, 0, [], 1, 1], "Cmp")'))
+    eq({0, {}, 1, 1}, meths.get_var('fl'))
+  end)
+end)