Correct error results.

Thanks mmatera!

mathics/builtin/strings.py

@@ -2099,8 +2099,8 @@ class StringTake(Builtin):
       <dt>'StringTake["$string$", {$m$, $n$, $s$}]'
       <dd>gives characters $m$ through $n$ in steps of $s$.
 
-      <dt>'StringTake["$string$", {$m$, $n$, $s$}]'
-      <dd>gives characters $m$ through $n$ in steps of $s$.
+      <dt>'StringTake[{$s1$, $s2$, ...} $spec$}]'
+      <dd>gives the list results for each of the $si$.
     </dl>
 
     >> StringTake["abcde", 2]
@@ -2134,11 +2134,21 @@ class StringTake(Builtin):
     #> StringTake["abc", {0, 0}]
     : Cannot take positions 0 through 0 in "abc".
     = StringTake[abc, {0, 0}]
+
+    #> StringTake[{2, 4},2]
+     : String or list of strings expected at position 1.
+     = StringTake[{2, 4}, 2]
+
+    #> StringTake["kkkl",Graphics[{}]]
+     : Integer or a list of sequence specifications expected at position 2.
+     = StringTake[kkkl, -Graphics-]
     """
 
     messages = {
-        "strse": "String expected at position 1.",
-        "mseqs": "Integer or list of two Intergers are expected at position 2.",
+        "strse": "String or list of strings expected at position 1.",
+        # FIXME: mseqs should be: Sequence specification (+n, -n, {+n}, {-n}, {m, n}, or {m, n, s}) or a list
+        # of sequence specifications expected at position 2 in
+        "mseqs": "Integer or a list of sequence specifications expected at position 2.",
         "take": 'Cannot take positions `1` through `2` in "`3`".',
     }
 
@@ -2173,8 +2183,9 @@ def apply_strings(self, strings, spec, evaluation):
         result_list = []
         for string in strings.leaves:
             result = self.apply(string, spec, evaluation)
-            if result is not None:
-                result_list.append(result)
+            if result is None:
+                return None
+            result_list.append(result)
         return Expression("List", *result_list)
 
 
@@ -2208,7 +2219,7 @@ class StringDrop(Builtin):
 
     messages = {
         "strse": "String expected at position 1.",
-        "mseqs": "Integer or list of two Intergers are expected at position 2.",
+        "mseqs": "Integer or list of two Integers are expected at position 2.",
         "drop": 'Cannot drop positions `1` through `2` in "`3`".',
     }