application/json GETs can have no request body.

spec/param_parser_spec.cr

@@ -30,18 +30,33 @@ describe "ParamParser" do
     params.should eq({"hasan" => "cemal", "name" => "serdar", "age" => "99"})
   end
 
-  it "parses request body" do
-    route = Route.new "POST", "/" { }
+  context "when content type is application/json" do
+    it "parses request body" do
+      route = Route.new "POST", "/" { }
 
-    request = HTTP::Request.new(
-      "POST",
-      "/",
-      body: "{\"name\": \"Serdar\"}",
-      headers: HTTP::Headers{"Content-Type": "application/json"},
-    )
+      request = HTTP::Request.new(
+        "POST",
+        "/",
+        body: "{\"name\": \"Serdar\"}",
+        headers: HTTP::Headers{"Content-Type": "application/json"},
+      )
 
-    params = Kemal::ParamParser.new(route, request).parse
-    params.should eq({"name": "Serdar"})
+      params = Kemal::ParamParser.new(route, request).parse
+      params.should eq({"name": "Serdar"})
+    end
+
+    it "handles no request body" do
+      route = Route.new "GET", "/" { }
+
+      request = HTTP::Request.new(
+        "GET",
+        "/",
+        headers: HTTP::Headers{"Content-Type": "application/json"},
+      )
+
+      params = Kemal::ParamParser.new(route, request).parse
+      params.should eq({} of String => AllParamTypes)
+    end
   end
 
   context "when content type is incorrect" do

src/kemal/param_parser.cr

@@ -38,7 +38,7 @@ class Kemal::ParamParser
   end
 
   def parse_json
-    return unless @request.headers["Content-Type"]? == APPLICATION_JSON
+    return unless @request.body && @request.headers["Content-Type"]? == APPLICATION_JSON
     body = @request.body as String
     json = JSON.parse(body) as Hash
     json.each do |k, v|