Prevent panic on empty tag/description (denisidoro#341)

Fixes denisidoro#339

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "navi"
-version = "2.5.0"
+version = "2.5.1"
 authors = ["Denis Isidoro <denis_isidoro@live.com>"]
 edition = "2018"
 description = "An interactive cheatsheet tool for the command-line"

src/parser.rs

@@ -164,7 +164,11 @@ fn read_file(
                 should_break = true
             }
             snippet = String::from("");
-            tags = String::from(&line[2..]);
+            tags = if line.len() > 2 {
+                String::from(&line[2..])
+            } else {
+                String::from("")
+            };
         }
         // metacomment
         else if line.starts_with(';') {
@@ -175,7 +179,11 @@ fn read_file(
                 should_break = true
             }
             snippet = String::from("");
-            comment = String::from(&line[2..]);
+            comment = if line.len() > 2 {
+                String::from(&line[2..])
+            } else {
+                String::from("")
+            };
         }
         // variable
         else if line.starts_with('$') {

tests/cheats/more_cases.cheat

@@ -44,6 +44,12 @@ echo "http://google.com?q=<query>"
 # fzf
 ls / | fzf
 
+# 
+echo description space
+
+#
+echo description blank
+
 $ x: echo '1 2 3' | tr ' ' '\n'
 $ y: echo 'a b c' | tr ' ' '\n'
 $ z: echo 'foo bar' | tr ' ' '\n'
@@ -57,4 +63,9 @@ $ multiword: echo -e 'foo bar\nlorem ipsum\ndolor sit\nbaz'i
 $ file: ls . --- --preview 'cat {}' --preview-window 'right:50%'
 
 # this should be displayed
-echo hi
+echo hi
+
+%
+
+# Without tag
+echo hi 1 2 3