Remove unnecessary FieldDoesNotExistException handling

Previously, FieldDoesNotExistException was caught when extracting
a field to determine whether or not it is missing (absent or an
empty collection). The handling is redundant due to an earlier call
to hasField so this commit removes it.

Closes gh-525

Author: izeye

spring-restdocs-core/src/main/java/org/springframework/restdocs/payload/JsonContentHandler.java

@@ -84,15 +84,10 @@ private boolean isMissing(FieldDescriptor candidate, Object payload) {
 		if (!this.fieldProcessor.hasField(candidate.getPath(), payload)) {
 			return true;
 		}
-		try {
-			ExtractedField extracted = this.fieldProcessor.extract(candidate.getPath(),
-					payload);
-			return extracted.getValue() instanceof Collection
-					&& ((Collection<?>) extracted.getValue()).isEmpty();
-		}
-		catch (FieldDoesNotExistException ex) {
-			return true;
-		}
+		ExtractedField extracted = this.fieldProcessor.extract(candidate.getPath(),
+				payload);
+		return extracted.getValue() instanceof Collection
+				&& ((Collection<?>) extracted.getValue()).isEmpty();
 	}
 
 	@Override