termwiz: allow degenerate empty parameter in iTerm2 protocol

The `bv` utility emits this slightly wonky sequence; since iTerm2 allows
it, we should also allow it.

refs: #1291

termwiz/src/escape/osc.rs

@@ -884,6 +884,11 @@ impl ITermFileData {
                 param
             };
 
+            // eg: `File=;size=1234` case. <https://github.com/wez/wezterm/issues/1291>
+            if param.is_empty() {
+                continue;
+            }
+
             // look for k=v in param
             if let Some(equal) = param.iter().position(|c| *c == b'=') {
                 let key = &param[..equal];

termwiz/src/escape/parser/mod.rs

@@ -1023,4 +1023,29 @@ mod test {
             ]
         );
     }
+
+    #[test]
+    fn issue_1291() {
+        use crate::escape::osc::{ITermDimension, ITermFileData, ITermProprietary};
+
+        let mut p = Parser::new();
+        // Note the empty k=v pair immediately following `File=`
+        let actions = p.parse_as_vec(b"\x1b]1337;File=;size=234:aGVsbG8=\x07");
+        assert_eq!(
+            vec![Action::OperatingSystemCommand(Box::new(
+                OperatingSystemCommand::ITermProprietary(ITermProprietary::File(Box::new(
+                    ITermFileData {
+                        name: None,
+                        size: Some(234),
+                        width: ITermDimension::Automatic,
+                        height: ITermDimension::Automatic,
+                        preserve_aspect_ratio: true,
+                        inline: false,
+                        data: b"hello".to_vec(),
+                    }
+                )))
+            ))],
+            actions
+        );
+    }
 }