callagent: Fix the parsing of responses without SDP part

callagent/MGCPResponse.st

@@ -59,6 +59,11 @@ Object subclass: MGCPResponse [
         | str |
         <category: 'creation'>
 
+        aDict isNil ifTrue: [
+            sdp := nil.
+            ^ self
+        ].
+
         str := WriteStream on: (String new).
         aDict second do: [:each |
             str

callagent/Tests.st

@@ -295,4 +295,13 @@ PP.PPCompositeParserTest subclass: MGCPParserTest [
         self assert: res sdp = sdp.
         self assert: (res parameterAt: 'I' ifAbsent: []) = '233434'.
     ]
+
+    testFailureResp [
+        | nl res |
+        nl := Character cr asString, Character nl asString.
+        res := self parse: '400 32323 OK', nl.
+
+        self deny: res isSuccess.
+        self assert: res sdp isNil.
+    ]
 ]