[TwilioAdapter] Ensure media retrieval does not throw KeyNotFoundException

[EricDahlvang]

Fixes: #2416

Ensure keys are present in the dictionary when creating attachments from a Twilio message containing media.

[coveralls]

Pull Request Test Coverage Report for Build 75951

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 348 unchanged lines in 50 files lost coverage.
• Overall coverage decreased (-1.9%) to 78.541%

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Files with Coverage Reduction	New Missed Lines	%
/libraries/integration/Microsoft.Bot.Builder.Integration.ApplicationInsights.Core/ApplicationBuilderExtensions.cs	1	71.43%
/libraries/Microsoft.Bot.Builder.AI.LUIS/LuisApplication.cs	1	95.45%
/libraries/Microsoft.Bot.Builder.Dialogs/Prompts/PromptValidatorContext.cs	1	82.35%
/libraries/Microsoft.Bot.Builder.Dialogs/WaterfallStepContext.cs	1	86.96%
/libraries/Microsoft.Bot.Builder/TelemetryLoggerMiddleware.cs	1	73.94%
/libraries/Microsoft.Bot.Builder.Testing/XUnit/TestDataObject.cs	1	82.35%
/libraries/integration/Microsoft.Bot.Builder.Integration.AspNet.Core/HttpHelper.cs	2	90.91%
/libraries/integration/Microsoft.Bot.Builder.Integration.AspNet.Core/ServiceCollectionExtensions.cs	2	94.94%
/libraries/Microsoft.Bot.Builder.AI.LUIS/Generator/DateTimeSpec.cs	2	64.29%
/libraries/Microsoft.Bot.Builder.Azure/CosmosDBKeyEscape.cs	2	89.74%

Totals
Change from base Build 75804:	-1.9%
Covered Lines:	4392
Relevant Lines:	5592

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💛 - Coveralls

[fuselabs]

✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.Luis.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.QnA.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.ApplicationInsights.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Azure.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Dialogs.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.TemplateManager.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Configuration.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Connector.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Schema.dll compared against version 4.3.1

[cleemullins]

Unit Tests for this are needed.

[EricDahlvang]

@cleemullins unit test added

[fuselabs]

✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.Luis.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.QnA.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.ApplicationInsights.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Azure.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Dialogs.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.TemplateManager.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Configuration.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Connector.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Schema.dll compared against version 4.3.1