Update doc for match: empty argument doesn't match anything

(cherry picked from commit 70ae6c21de9fd3f0e00a052b15f70c3667836898)

doc/classes/String.xml

@@ -499,14 +499,14 @@
 			<return type="bool" />
 			<argument index="0" name="expr" type="String" />
 			<description>
-				Does a simple case-sensitive expression match, where [code]"*"[/code] matches zero or more arbitrary characters and [code]"?"[/code] matches any single character except a period ([code]"."[/code]).
+				Does a simple case-sensitive expression match, where [code]"*"[/code] matches zero or more arbitrary characters and [code]"?"[/code] matches any single character except a period ([code]"."[/code]). An empty string or empty expression always evaluates to [code]false[/code].
 			</description>
 		</method>
 		<method name="matchn">
 			<return type="bool" />
 			<argument index="0" name="expr" type="String" />
 			<description>
-				Does a simple case-insensitive expression match, where [code]"*"[/code] matches zero or more arbitrary characters and [code]"?"[/code] matches any single character except a period ([code]"."[/code]).
+				Does a simple case-insensitive expression match, where [code]"*"[/code] matches zero or more arbitrary characters and [code]"?"[/code] matches any single character except a period ([code]"."[/code]). An empty string or empty expression always evaluates to [code]false[/code].
 			</description>
 		</method>
 		<method name="md5_buffer">