fix nimsuggest crash with arrow type sugar (#24185)

fixes #24179 

The original fix made it so calls to `skError`/`skUnknown` (in this case
`->`, for some reason `sugar` couldn't be imported) returned an error
node, however this breaks tsug_accquote for some reason I don't
understand (it even parses as `tsug_accquote.discard`) so I've just
added a guard based on the stacktrace.

compiler/semexprs.nim

@@ -890,6 +890,9 @@ proc analyseIfAddressTaken(c: PContext, n: PNode, isOutParam: bool): PNode =
 
 proc analyseIfAddressTakenInCall(c: PContext, n: PNode, isConverter = false) =
   checkMinSonsLen(n, 1, c.config)
+  if n[0].typ == nil:
+    # n[0] might be erroring node in nimsuggest
+    return
   const
     FakeVarParams = {mNew, mNewFinalize, mInc, ast.mDec, mIncl, mExcl,
       mSetLengthStr, mSetLengthSeq, mAppendStrCh, mAppendStrStr, mSwap,

nimsuggest/tests/tarrowcrash.nim

@@ -0,0 +1,20 @@
+# issue #24179
+
+import sugar
+
+type
+    Parser[T] = object
+
+proc eatWhile[T](p: Parser[T], predicate: T -> bool): seq[T] =
+    return @[]
+
+proc skipWs(p: Parser[char]) =
+    discard p.eatWhile((c: char) => c == 'a')
+#[!]#
+
+discard """
+$nimsuggest --tester $file
+>chk $1
+chk;;skUnknown;;;;Hint;;???;;0;;-1;;">> (toplevel): import(dirty): tests/tarrowcrash.nim [Processing]";;0
+chk;;skUnknown;;;;Hint;;$file;;11;;5;;"\'skipWs\' is declared but not used [XDeclaredButNotUsed]";;0
+"""

tests/errmsgs/tundeclared_routine.nim

@@ -9,7 +9,7 @@ tundeclared_routine.nim(29, 28) Error: invalid pragma: myPragma
 tundeclared_routine.nim(36, 13) Error: undeclared field: 'bar3' for type tundeclared_routine.Foo [type declared in tundeclared_routine.nim(33, 8)]
   found tundeclared_routine.bar3() [iterator declared in tundeclared_routine.nim(35, 12)]
 tundeclared_routine.nim(41, 13) Error: undeclared field: 'bar4' for type tundeclared_routine.Foo [type declared in tundeclared_routine.nim(39, 8)]
-tundeclared_routine.nim(44, 15) Error: attempting to call routine: 'bad5'
+tundeclared_routine.nim(44, 11) Error: undeclared identifier: 'bad5'
 '''
 """